Stoneguard mobs are unable to pathfind through the limestone doors found in pyramids, single or double, and possibly more doors.

That is intended. Stoneguards are not smart enough to open doors.

Seems to be a vanilla issue. Zombies etc. can't walk through any open doors either.

Oh sorry I guess I wasn't clear, I meant you can open the doors and a stoneguard can be in the room and it pathfinds right to the door where you can hit it through the open door but it cant pass through for some reason

Oh I misunderstood then.
I'll take a look at it, but it's most likely just because of vanilla mobs having issues with doors in 1.12