Each situation is different. All we can really do is be careful not to say no / break a shidduch for a dumb reason – if there’s a question ask daat torah – and pray that Hashem guides us to the right decision.
And I agree – don’t judge! It’s not fair when people automatically “black-list” someone because they were engaged before. Look into it, from a reliable, honest source. In some cases it may be something to worry about, but I believe in most it really was just an unfortunate situation – they were pushed, etc. There are a ton of cases where one or both sides were pushed to continue/move fwd and didn’t realize until it was (almost) too late, that it wasn’t the one for them. We should never know! So please don’t judge.