No Debug information

Hi all.

I have an old problem in a project and it keeps popping up now and then. I think the problem is related to a UART driver I wrote.
On the UART I have GPS and modems. Now and then I have errors on these devices and sporadically the system goes into the watchdog.

If I try to debug when I have errors on the GPS I often get the attached error.

How can I proceed?

Best Regards