It's very hard to keep up with because there are new incidents every month.
You could start with the
Howard Jacobson article from April to get to grips with what British Jews actually feel about the issue.
The major flashpoints around Corbyn involve his appearances on Press TV and muttering antisemitic tropes, praising an antisemitic mural, laying a wreath on the grave of the mastermind behind the Munich attacks and a list of other incidents involving Holocaust deniers and general antisemitism that is far too long for me to link up at work.
Most people here think it's a conspiracy but it absolutely isn't. The leaders office is doing absolutely everything it can to protect blatant antisemites. They'll tell you it's because he cares for Palestinians, but then why is he taking Assad's money? He thinks a Jewish conspiracy is responsible for most of the world's ills and the criticism he receives. Last month Thornberry said he failed to deal with it because he was 'upset'.
The long and short of it is that Corbyn brought in an influx of people from notoriously antisemitic parties and has been trying to protect that voting bloc in the membership ever since.
Worth remembering at this point that Israel only exists because of Labour and Clement Atlee.