Hmm, perhaps I should reopen the ticket, even though I now found the cause.

After all, it is possible that lineno is None and inspect.getframeinfo() cannot handle it :-)

And it may be worthwhile investigating why recreation of a code object using:

            return types.CodeType(co.co_argcount,
                                  co.co_posonlyargcount,
                                  co.co_kwonlyargcount,
                                  co.co_nlocals, co.co_stacksize,
                                  co.co_flags, co.co_code, co.co_consts,
                                  co.co_names, co.co_varnames,
                                  co.co_filename, co.co_name,
                                  co.co_firstlineno, co.co_lnotab,
                                  co.co_freevars, co.co_cellvars)

does not necessarily create a valid copy of a code object co.