A new article posted in Embarcadero blog.

https://blogs.embarcadero.com/upgrading-cbuilder-12-2-tip-5-split-out-eh-and-seh-exception-handling/

They say, the new bcc64x compiler now doesn't allow mixing C++ EH and extended SEH in "SAME FUNCTION" while old compilers allowed.

And they advise splitting two kinds of exception handling to other function.