Direct answer
For the iRobot Roomba s9/s9+, lighting, sensors, map state, floor transitions and environmental traps matter more than repeated factory resets. First, clean approved sensors and run a small mapped area.
What this covers
- iRobot Roomba s9/s9+ (s9, s9+)
- iRobot Roomba; mapping, obstacle avoidance, self-emptying and mop functions vary.
- The specific fault this record addresses: robot vacuum gets lost, stuck or misses rooms
What it does not cover
- ×The same symptom on a different iRobot product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
Low light or inconsistent lighting is affecting optical sensors
What separates it Navigation problems happen at specific times of day or in specific rooms with unusual lighting, and are absent in well-lit conditions.
How to confirm Run a cleaning cycle during consistent daytime lighting as a comparison against the problem time.
- 2
Mirrors, glass, or dark surfaces are confusing distance sensors
What separates it The robot gets stuck or behaves erratically near a specific piece of furniture, a mirror, glass door, or a dark rug.
How to confirm Remove or temporarily block that specific object during a test run to confirm it as the cause.
- 3
Cords, low-hanging fabric, or small objects are trapping the robot
What separates it The robot gets physically stuck in the same location repeatedly, rather than avoiding rooms entirely.
How to confirm Clear cords, blind cords, and small objects from that specific area before the next run.
- 4
A floor-height transition (thick rug edge, high threshold) is stopping the robot
What separates it One specific room or zone is consistently skipped or the robot backs away at the same threshold every time.
How to confirm Test the transition manually — a threshold above the model's stated maximum climb height will need a ramp or the room accepted as out of reach.
- 5
The stored map has become outdated after furniture or room changes
What separates it A previously reliable robot suddenly starts missing rooms or getting lost after furniture was moved or rearranged.
How to confirm Rebuild the map for the affected area only, preserving other saved rooms and schedules where the app allows a partial rebuild.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- Whether the problem is tied to a specific room, object, or time of day, versus happening everywhere unpredictably.
- Whether the robot gets physically stuck in place, or avoids/skips an area without ever entering it.
- Whether furniture or the dock's position changed recently.
Clean approved sensors per the manual
ReversibleDust on optical or cliff sensors can cause the same symptoms as an environmental problem.
Run a small mapped area as a controlled test
ReversibleIsolates whether the issue is room-specific or global.
Remove cords, mirrors and other identified variables one at a time
ReversibleConfirms which specific object or condition is the actual cause.
Rebuild only the affected portion of the map after correcting the environment
ReversiblePreserve other saved rooms and schedules where the app supports a partial rebuild.
Complete two full runs to the same previously problematic rooms
ReversibleConfirms the fix holds rather than being a one-time success.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- s9, s9+. iRobot Roomba; mapping, obstacle avoidance, self-emptying and mop functions vary.
- Type — ROBOT vacuum (D-shape)
- A high-end ROBOT vacuum with a distinctive D-shape front for better corner and edge cleaning, and a Clean Base self-empty dock — symptoms are navigation, docking, brushes and the base.
- Clean Base self-empty
- Empties into the Clean Base dock; 'won't empty' is a full bag or clogged path, 'won't dock/charge' is dirty contacts, a moved/unplugged dock, or blocked clearance.
- Brushes, wheels & sensors
- Wider dual rubber brushrolls, a corner side brush, drive wheels and sensors — clear hair and wipe sensors if it gets stuck, circles or misses areas.
- Symptom boundary
- This record covers iRobot Roomba s9/s9+ when it robot vacuum gets lost, stuck or misses rooms. A different symptom on the same hardware, or this symptom on a different iRobot product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Protect stairs and known hazards independently of the robot's own sensors — do not rely on a robot vacuum's cliff detection around stairs, pools, or similar drop-offs as the only safeguard.
- !Do not rely on the robot around pet waste or liquid spills; these can be spread across a floor rather than cleaned.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. iRobot Support publishes this as "Roomba support". Official Roomba setup, error, mapping, cleaning and repair support. What that article does not carry is the model boundary — it is written for a product line, and s9, s9+ is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
My Roomba s9 isn't picking up as well as it used to.+
Clean the moving parts. Pull the two rubber brushrolls and clear hair from them and their end bearings, remove hair from the side brush and the front wheel, and empty/clean the bin and its filter (tap out the filter; do not wash iRobot filters). Wipe the sensors. On the s9, corner and edge pickup depends on the side brush spinning freely, so a hair-bound side brush is a common cause of dust left along edges.
The robot gets stuck in the same spot every time.+
Check that specific location for cords, low-hanging fabric, small objects, or a floor-height transition like a thick rug edge — a robot repeatedly failing in one exact spot points to something physical there, not a general navigation fault.
It used to map the whole house fine but now it's missing rooms.+
This usually follows furniture being moved or rearranged. Rebuild just the affected portion of the map rather than starting over completely — most apps support a partial rebuild that preserves other saved rooms and schedules.
Does this answer apply to every iRobot model?+
No. It is scoped to s9, s9+. iRobot Roomba; mapping, obstacle avoidance, self-emptying and mop functions vary.
What should I record before troubleshooting gets lost or misses rooms?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing gets lost, misses rooms. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Protect stairs and hazards; do not rely on the robot around liquids or pet waste.
Answer for the exact device and software version shown above.