UPDATE
Having looked at this machine in detail i may have identified the grinding problem..... the two optical sensors which are standard on about every cnc machine ive ever worked on , are both fine. the flags used to trigger them are just 4mm bolts which have been painted with what i suspect is black marker in an effort to make them work with the sensors, the black very quickly comes off, condensation etc, my initial test will be some heat shrink over the bolt if that works ill make proper flags.
ok so, the swap
mine has the awful grinding noise (more later)
i decided to look at this myself rather than trying to get square off to actually do anything.
disassembly. This board was NEVER intended to be taken apart, not even by the factory. you have to remove the high quality playing surface (CARDBOARD) which is fixed down with very aggressive tape, at a guess i'd say carpet tape. Once you have spend a good few hours doing that and cleaning the tape residue you have access to the 10 screws fixing the top to the base. How you can build a complex and expensive product without a relatively simple means of disassembly completely escapes me, square off Obviously had no intention of ever repairing these or even allowing anyone else to repair them.
My new top will probably be acrylic this sheet with the screw holes ready cut.
the grinding noises.....
the cnc mechanism is two radial arms, there are two optical sensors to allow the arms to locate a datum point, as they are scanning for the sensors the arms go into a reducing throw wiggle to pinpoint the datum at the sensors, this wiggle regularly locks up into a grinding noise, its not actual grinding its just a high speed oscillation. cause FIRMWARE. without access to the actual firmware i dont see any fix for this and i doubt anyone will ever get that.
i think the swap should have stayed with the linear motion cnc which was fairly reliable.
the whole view i get is that of a brilliantly conceived idea which has been totally rushed into production taking so many shortcuts all of which are at the cost of the customer.
if you have a swap thats demonstrating any of its "foybles" either fix it yourself or bin it.