We still don't know if the microcode is faulty or not, we only know no one of the other packages is.
The way to know right now, take the microcode update and cross fingers.
Considering it's a new install and there are snapshots, I'd go for it.
In case it was the culprit, restore snapshot, reboot, and temporarily add IgnorePkg = intel-ucode to /etc/pacman.conf until a new one comes out, then remove that line.
Or, you may blindly do that now, but in this case you'll never know for sure.
If you have to restore a snapshot, watch out for this problem (disregard my comment there...)
How do I remove snapper backup images? - #3 by Kiss-my-axe