PL/SQL ERROR 801 when compiling form in 12c that compiles in 11g

We are moving from 11g to 12c.  A number of forms that compile with no problems in 11g produce the following error message when compiling in 12c:  PL/SQL ERROR 801 at line 150, column 1 internal error [*** ASSERT at file pdz2.c, line 5072; Cannot write IDN value to an external Diana node 196645; XNSPC0LOC_CHECK_RECORD__B[150, 1]] They also produce files with names like XNSPC0LOC_CHECK_RECORD__B.plz which I am not allowed to attach.  What could be causing this problem?  By the way, where in the documentation is a list of all the PL/SQL errors and hints to resolve them?