Part of the problem is that the Labour Party's internal disciplinary processes, in seeking to be fair, are also cumbersome and long-winded. (The process was once described by a prominent Labour figure as "12 people taking a year and 10 meetings to decided who told who to fuck off"). Adherence to the rules means that swift action isn't possible.
I've no doubt that there are some anti-Semites in the party. It's a large organisation, and any large organisation will include some people with anti-Semitic (or racist, sexist, or homophobic views).
The waters are muddied by the efforts on the part of a section of the Jewish community to dismiss any criticism of Israeli expansionist policies in Palestine as anti-Semitism. It's a rather crude way of trying to shut down debate.
The Labour party is a much younger organisation than it used to be, and no-one much under 50 will remember the days before the illegal expansion beyond the 1947 borders. That perhaps accounts for more anti-Zionist sentiment on the left. Let's not forget that the left was in the vanguard of fighting against anti-Semitism in the 1930's, and I've no doubt that if the fascists were to march down Cable Street again, inciting up hatred of the Jews, the left would once again be out in force to defend them.
Israel has always been a tricky issue for those who believe that state and religion should be separate entities, which is a pretty mainstream position on the left. I think that people who once would have felt that Israel was a special case are losing patience because of what has been happening in Palestine and now questioning whether a Zionist state is such a good idea.
Anyway, I think the furore is being stirred up in an attempt to discredit Labour. I strongly suspect that the numbers of genuine anti-Semites in the Labour party are fewer than the numbers of racists in the Tory party. After all, look how they behaved towards the Windrush descendants.