Yeah I've been seeing this for a few months now.

My workaround is to upvote threads I've read, since it's doing a better job of remembering what I've voted on.

Is there still no fix to this?

I was just coming to mention this. We are nearing the end of being able to use sync. I don't use it enough to try using another app but hopefully he's working on something

Same here, I've already clicked on multiple links and only realized after seeing a comment that I had read that I had already seen that same thread. Very annoying.