Are converts to Judaism *always* accepted?

I don't know the story behind this business about conversions being cancelled - all sounds a bit strange. But in general, apart from the problems you know about, with Orthodox not accepting Reform conversions, I really haven't ever known anyone to question or be non-accepting. Obviously my experience is limited - to the UK, to London and one other city in the UK and to only the people I've come across. But no-one I've ever spoken to has suggested there is any problem here in the UK. Since it is the Beit Din who actually accept someone as being Jewish, and one goes in front of them for them to make that decision, I'm not clear how a Beit Din can decide they were wrong in the first place! The rabbi merely decides and declares their readiness in her/his opinion but it's up to the Beit Din to make the decision.