EBS R12.2.7 : objects gets invalidated

Hello,

We are in process of upgrading EBS to R12.2.7 from 11i.    We have upgrade couple of non prod environments  and developers are in process of modifying custom objects  .     We are seeing random behavior of invalid objects.

After we recompile apps schema  we have 65 invalid objects.   However ,  if we look at it again after couple of days,   the invalid object count increases to   2000+  /  3000 +   etc.     We need to keep on recompiling every few days.   We are trying to understand , why the objects get invalidated.

Please advise

Thanks

Ram