They may always have a 2064 when wired discretely. Sounds like it isn’t seeing the open limit, does it ring out? And do you see the DOL LED on the UIT interface board? If so, do you see it in the actual door board underneath? They can be wired different ways but maybe the serial comm failure is between the 2 boards and the limit not getting from the top to the bottom. Not sure though, don’t really see those on anything but TK controllers.