Hello,
Firstly, I'd recommend updating to the latest firmware, as no issues similar to yours have been reported on it.
If the reboot from the WebUI does not help, then there aren't many other options than physically plugging the power cable out.
You could try logging into the device via CLI and run this command, which will reset the switch:
swconfig dev switch0 set soft_reset 1
Let me know how it goes.
Best regards,
DaumantasG