Device forces reboot when starting LuCI WebUI

Hello,
I have completed setup of device Mikrotik hEX S (RB760iGS) with OpenWrt OpenWrt 22.03.0-rc5.

There are no issues until I configured extroot.
This means when I try to open WebUI the router is performing a forced reboot.
Observing syslog with logread -f shows no errors before the reboot.

Can you please advice how to start analysing this issue?

THX

but it works just fine if you don't use exroot ?

Yes.

And I have identified that it works after reboot w/ extroot.

However, I want to analyse this issue, and need some advise here.
Syslog, that is written to memory, shows nothing related to the issue.

Basically I need a log that records anything related to kernel, services, etc.