This is only my opinion. Malwarebytes is not a replacement for a virus scanner. It is a malware scanner and can some times pickup malware that AV could miss.
Did you manually disable Defender or did it disable automatically when you installed Malwarebytes.
If you take out the bios battery it will reset the bios and it will reset every time you power off if you leave it out. The time will go back to default and windows may not correct it for a few minutes after the OS starts.
You can take out the battery to reset the bios and it may need some settings changing once you put it back.