I’ve got a similar problem. Though to the other side. It took a long time but I found my bad ankle ROM (on high side) was probably the culprit. It’s ongoing, my squat unloaded looks even now, but going over head things can get ugly if I haven’t warmed up. I feel very tight almost nervy through my tricep
I figure, just keep working on better ankle ROM, clearing hip impingment and position while over head and my tight tricep will obey….
This has worked for me so far, might be useful for you also?