When compiling some of your "working" code, you may also now see this message:
IBM2621I W ON ERROR block does not start with ON ERROR SYSTEM.
An error inside the block may lead to an infinite loop.
The new compiler will produce this message for any ON ERROR block for which does not start with the statement ON ERROR SYSTEM. If an ON ERROR block does not start with this statement, then if there is an error in the ON ERROR block, the block will most likely be reentered and an "infinite" loop would result.
Code that produces this message should be corrected.