v4.1 to v4.2 - esp_timer issue

[leemoore1966]

Hi All
I have a large codebase running on v4.1 of esp-idf.
I need to add a feature that requires moving to v4.2

If I rebuild my code under v4.2, when I run I keep getting a PANIC in the esp_timer thread

Firstly, I do not start this thread, so I am assuming this is a system level thread.

I do not have access to a idf.py monitor, as I need to re-purpose the UART usually used for the monitor, for one of my sensors, and all other UARTS are in use.
I do have complete debug access using gdb(ddd)/openocd

I can see all of my thread data, and I can see the esp_timer thread currently locked up

I have no clue how to debug how I got here, this only occurs when using v4.2, under v4.1 I have no issues.
I looked at the differences in the code for the esp_timer, as far as I can see, the only real difference is that one of the function return types has switched from an unsigned 64bit, to a signed 64 bit

I am really clutching at straws how to progress this - I need to get it working on v4.2, but I cannot see what in my code is causing this to happen
any advice greatly appreciated

Thx
Lee