Debris picked up from the bottom of the pool leaks out on removal

by Maggie
(Charleston)

When I finish cleaning the pool with the diagnostic Dophin Robot I lift the unit out of the pool. Debris picked up from the bottom of the pool leaks out. What is making this happen? I remove the bag and dump the contents and spray the bag with clean water; there is plenty of
debris in the bag.
I just read a previous complaint with this problem and the admin said the flap on the intake could be missing or stuck. Mine is not missing. How do I fix it if it is stuck?