Lego 42129 - issues with rear wheels

I am currently building the zetros truck and I am experiencing an issue with the rear wheels. Once the diff is locked the rear wheels spin just fine. It does look like left is turning slower then the right rear wheel but it at least turns. Once the diff is unlocked the left rear wheel gets stuck and won’t turn. I am kinda lost now with where to look or check. Hoping someone has the experience or knowledge to tell me what to do and what to check. submitted by /u/s1abc [link] [comments]