I second the above - combined handbrake and brake calipers on the other models (most 200, 400, 600, 800 and later variants of such where applicable) are awful for seizing - I've owned lots of MGR vehicles over the years, and by far the vehicle with the most reliable handbrake system is the 75 / ZT.
Fond memories of having a cherry red glowing rear disc on my first 620ti - and then similar issues with a ZS, a 45, another 620ti... very common, and in part down to poor maintenance (regular brake fluid changes would help prevent the piston corrosion that causes this) but also an inherently weak design it seems.
FYI, for anyone struggling with the handbrake efficiency on the 75 / ZT, there are a number of common causes - most prominently the Handbrake Compensator (Arctic supplies a modified version that doesn't stretch), the Brake Shoes not making full contact with the inside of the drum as some aftermarket shoes seem to be the wrong shape (we have originals here:
https://www.dmgrs.co.uk/products/gen...-p-n-sfs100190 )
Finally, the backplates rust through allowing the pins to slip through the plate itself - have had this happen twice so far.
Luckily a set of pre-assembled backplates with everything needed won't break the bank:
https://www.dmgrs.co.uk/products/r75...0290-smn000140
While quite a complex design on our cars, it does seem to do the job well when working correctly.
