Just the one you dug up on the MalwareBytes forum
. They're led to believe that the issue is MB initially, from some other source, but they also have Avast, as you've read.
Unfortunately that doesn't mean a whole lot. I know you're not big on IT repair shops, and it sounds like you've had to deal with overcharging cowboys before but having multiple AVs is a big red flag to me and I think anyone worth their salt would pick it up. Hell I tend to check for bad/incomplete uninstalls of old antivirus software as well.
Again, no problem with using 1 Antivirus program & then MBAM on top in a strictly "on demand" scan, with no active protection. This just applies for two AVs actively fucking around in kernel space.
Rule them out. You're one motherboard replacement in and were ready to sell your parts and start again, man.