I think the stories about problems around the Peterborough poll are a lot more than just tittle tattle. Whether there was significant interference enough for the poll to be rerun I have no idea
But I think that Labour have been unconscionably careless in their approach to this byelection, considering what caused it. The chosen candidate may or may not have seemed to endorse anti-semitic comments, but they should have checked, double checked and triple checked the candidate to make absolutely sure whoever was chosen was careful, if not pedantic about checking everything they commented on. The campaign manager should also not have allowed anyone with a conviction for election fraud anywhere near Peterborough, let alone as part of the Labour election team, even as an unofficial volunteer.
Given how sensitive this byelection was because of the behaviour of the ousted MP, you would expect any party in that situation to be being very careful about everything they did around the election. Perhaps the Labour Party was and this sloppiness was typical of the way the party is run at present.