Unfortunately the problem still exists. 
The machine just rebooted spontaneously running on battery power.
Running connected to power, I got the following different in the kernel messages (from dmesg):
[ 2235.394683] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2235.446680] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2263.082335] power_supply_format_property: 1 callbacks suppressed
[ 2263.082342] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2263.126335] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2263.174345] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2263.218488] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2263.254338] power_supply BAT0: driver failed to report `voltage_now' property: -16
[ 2263.294619] power_supply BAT0: driver failed to report `voltage_now' property: -16
Connected to power, I’ve not experienced a spontaneous reboot.
Not sure if this is related but the problem occurs now when running some large compile job (load avg 8).
I am at:
- linux: 6.15.4-mnt-reform-arm64
- sysfw: PREF1SYSR120250623
- hid: PREF1HID20250623
edit for reference: it seems this issue is related: pocket reform/rk3588: brownout at 2x3.6V (#33) · Issues · Bugs / Bugs · GitLab