Presumably this is a bug, so just reporting it. A chap in my race tonight somehow managed to sandbag in two separate categories at once. He’s a B and was filtered on ZwiftPower from both cat C and D races with identical stats and exactly a minute between his times (presumably reflecting the staggered start times).
Ordinarily I would guess at this being a ZP bug - hence posting it here - but he’s on both sets of ‘official’ results on the Companion app too. Weird.