Xiaomi Redmi Router AC2100 Random restarts on OpenWrt 21.02.1

|Model|Xiaomi Redmi Router AC2100|
|Architecture|MediaTek MT7621 ver:1 eco:3|
|Firmware Version|OpenWrt 21.02.1 r16325-88151b8303 / LuCI openwrt-21.02 branch git-21.295.67054-13df80d|
|Kernel Version|5.4.154|

My router is experiencing random reboots.
This seems to only happen with the "stable" release.
Does not seem to happen on snapshots.
I am unable to identify if anything is wrong from dmesg or logread - think the log is lost once rebooted.

How do I troubleshoot?