I'm Jewish and, to my mind, the Labour antisemitism thing is both true to some extent and also weaponised by the media/RW to put down the idea of a socialist political party.
People like Corbyn believe they are the good guys and antiracist, therefore they cannot be antisemitic. But at the same time they are just that bit taken in by Zionist conspiracy theory and the idea that Jews are a bit too 'powerful', rather a lot more interested in criticising Israel (and believe me, it deserves criticism) than anywhere else that abuses human rights and so on.
They are not to be compared to the Nazis or any nonsense like that - there's no existential threat at all to us to my mind. But still there's a strong cohort in Momentum that doesn't really trust Jews, IMO. Not because Momentum inherently antisemitic, but unfortunately the far left does attract that fringe that thinks Bankers (aka Jews) control the world etc.
TBH I think a big part of the problem is that Corbyn just isn't that bright. I know he might give this impression of being intellectual magic grandpa, but really he's quite blinkered and knows what he knows, and doesn't know an awful lot about Jews, so has fallen into antisemitism and associating with antisemites.
It is unfair that the media focuses only on Labour's antisemitism without comparing it to anyone else's, as sadly there's a lot of it about.