The backtrace points to the line that has:
``` PL_exit_flags |= PERL_EXIT_DESTRUCT_END; ```
Which suggests that global variable from Perl lib `PL_exit_flags` is messed up. You can check it with gdb -- open the core file with:
``` gdb /path/to/kamailio /path/to/corefile ```
Then run:
``` p PL_exit_flags ```
The crash happens during the reload, which might be done periodically, a matter of the modparam. You can try to disable it and see if the still crash happens. This periodical reload tried to help with Perl interpreter and libs memory leaks, so watch the system memory as well to be sure it not increasing without an obvious reason.