I also had all four bolts come off on a Rover mower disc one time, which has me baffled to this day. I had only just put them back on and had tightened each bolt fully. I had a mulcher plug fitted in the rear and was mowing some very heavy, soft clover, which contained a lot of moisture. I went three rounds of the lawn and next thing the entire blade disc dropped off and almost burrowed itself into the dirt underneath. I could not believe it. Every bolt had unwound until they had fallen off. I've never had that happen before and it has never happened since. I put it down to Gremlins.
They should have just done it the Victa way with one large nylock nut with locator tabs built in, but no, they are too proud and have to do it their own more complicated way for the sake of it.
Any wonder Victa were so popular. Simple and proven.
