D20 Pro Plus not returning to base when full

I am a new D20 Pro Plus user and I really like it so far, but a problem we've experienced with our first few cleanings is that when the D20 collection chamber fills up, rather than returning to base to empty itself, it starts depositing clumps of dust/fur behind itself like little D20 poops. The D20 does empty successfully when it returns to base, with an audible thwoop as the collected material is sucked up. 

It looks like the D20 is not returning to base mid-cycle if the collection chamber is full. Is this something it is expected to do? Is it a setting? Any suggestions would be appreciated.  Obviously I could have it do smaller cleaning tasks by manually selecting one room at a time or similar, but I bought this with the hope that it will be fairly autonomous.