Hi,
We faced the same error after upgrade. But you didn't put complete dump here.
Our short text was "Access using a Zero object reference is not possible'.
When you 'Check' DTP it would say Transformation does not exist.
When activating through program RSDG_TRFN_ACTIVATE it would say Error creating version A.
But when activating transformation manually in Dev it worked ok. So we sent transport to all further systems and solved the problem.
Regards