There have been mag failures where the Bendix mag came loose because the bolt holding its retaining bracket came loose.
As Pilot-DAR says, it isn't wirelocked, which is stupid, especially if it is one of these which, if it works loose, stops the engine totally.
They're not the same thing - you can't lock a screw if it's sitting in a recess or has a countersunk head. The magneto-to-accessory case nuts have locking washers to secure them; wirelocking is completely impracticable in most cases because of access. I actually installed a magneto today on an IO 540 and you can barely
see the inner clamp nut, never mind wirelock it.
I'm puzzled as to why you weren't happy with the Form 1 that the overhaul facility supplied with your magneto, Peter337 (and I know which company it is; we use them all the time and they're excellent in all respects...) - the paperwork certifies that the overhaul/repair has been carried out iaw procedures and all SBs/ADs have been complied with.
Apropos of wirelocking, it's not always necessary on aircraft: look at your cylinder base nuts. Many hydraulic, fuel, oil and pneumatic hose couplings aren't locked either.