QUICK ANSWER
Start with the dirty-water tank and wash tray.
These are the safest user-serviceable points to check when water remains in the dock.

INTERACTIVE DIAGNOSIS
Why is water staying in the tray?
Is the dirty-water tank empty, fully closed and firmly seated?
Do not keep flooding the tray
If water continues accumulating after the visible checks, stop repeated wash cycles and arrange service.
OFFICIAL REFERENCE
Dreame dirty-water troubleshooting
Dreame’s guidance covers the sewage outlet, washboard sensors, used-water-tank seals and correct tank seating.
Open official Dreame guidance