Xteink X3 from Taobao

I bought a mainland China version of this device via a friend, and overall it works normally, but I can't get any button combinations to work.

Whenever I try pressing Power + Volume Up together to reset or restart (following standard tutorials) the device completely ignores the input. There's no freeze, popup, or reboot screen; it just keeps running as if nothing was pressed.

The strange thing is that both buttons work perfectly fine individually for turning off the screen, adjusting volume, or switching pages. Has anyone with the CN version run into this issue? Is multi-button combo support disabled on this firmware, or is there a different trick/shortcut to force a restart?