Yes WOFF models random failures, and those aircraft that had poor reliability are also worse than others in the sim.
Bad0pel, fly 100 missions then come back and say how often it happens. Random is random
you can have 10 in a row then none for 10 years
Same with any oddity in WOFF you need to sample a lot more before calling something really.
Spad V.II's have poorer reliability than the general aircraft - gearing issues (maybe from the paint as Robert says?) same engine with problems as SE5, as do early SE5 and several others (cough Fokker EIV).