I identify as a left-wing person and I have never seen (in the limited circles of people I know) an anti-Jewish comment that wasn’t immediately called out as such.
I think left-wing critics of Israel’s expansionist policies who, mistakenly or deliberately, conflate Israel with Jewish people and then go on to say anti-Jewish things stop being part of the left (on race issues) the moment they do it. Just as a Conservative voter who speaks in support of the NHS (socialised medicine) stops being part of the right (on that issue) when they do so.
Just about every human organisation, from friendship groups to workplaces need to be ever-vigilant against all forms of racism, and haven’t done enough to combat it – the evidence being that racism still exists – but I don’t see anti-Semitism (or other forms of racism) arising from any part of left-wing doctrine, as I understand it.
Here’s an exchange I saw on Twitter, to take the edge off.