QUICK ANSWER
First decide whether it never starts or empties poorly.
Roborock says auto-empty can be disabled by settings, DND, manual docking or returning without cleaning. Poor emptying points instead toward the bag, brush installation or blocked airflow.

INTERACTIVE DIAGNOSIS
Find the auto-empty failure
STEP 1 OF 3
Does the dock start the emptying motor at all?
Test after a normal cleaning run and let the robot return to the dock itself.
Avoid probing the powered suction dock
If settings and visible airflow checks pass but the emptying motor remains inactive, disconnect the dock and use qualified service rather than opening its powered components.