If MMC have never seen it before then my guess would be that in production the bolts are supposed to be secured with Loctite and for some reason it didn't get applied in this case?
In any circumstance, safety-critical fasteners should always have some sort of security be it lock nuts, tab washers, lock wire, or a bonding agent used.
Tim H. 1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE
