Cortex A9 freezing

Hi All

I'm having a problem with my A9 based system (Zynq 7000) freezing occasionally, to a point that JTAG can't halt the processor. The issue isn't easily repeatable and when it does happen no debug info can be extracted. The only thing that can be read is the program counter, but even that seems all over the place with different locations for different instances.

First question - what could possibly lead to a critical failure like that? My thinking was around interrupt return address becoming corrupt somehow, but it's just guesswork at the moment.

Second question - how to arrest the problem, so I can at least see the stack trace? Any register I can set a hw watchpoint on?

Any comments are appreciated.