How to dispose a MWStructArray contains dataset from JAVA MCR

I use JAVA MCR to load matlab object from file (or generated them from MCR call), then I will dispose the MWStructArray after some work. It work most of case, MCR release the memory (the memory consumed by the java process will do down). But when the matlab struct contains lots of dataset object in its fields, dispose the MWStructArray will not release memory. Is this a bug? Any special code can release the memory?

I use matlab runtime 2016a