Cheating

[Imp]

I don't have a problem with WinSPWW2 ambushes/OP fire.

Op fire is reliable if your firing unit is not suppressed, and has not moved

That was my point its no good trying to spring an ambush with fast moving/suppressed units they want at least to start the turn stationary for a good result.
Otherwise the unit does not fire because it deems its chance of being effective as to low or even worse because it has not seen it.
They did not fire the PF Piat etc because it would be a wasted shot as the chance to hit is remote. If they have been sitting waiting so setup they will have a go as now operating effectivly simples.