Maybe you are right !
I never had any back pain while deadlifting but I can't do squat anymore
just unracking the bar, something pinches a nerve in my lower back and it hurts like hell.
Even with 135 lbs
I had a similar problem for nearly 3yrs, Stavios. I couldn't touch 185 or else I would feel my back pop. I could deadlift, do lunges and hack squats, but no Back squats. Front squats were iffy, but usually a no go.
One day I got a massage hoping that would cure the issue, and just hoped it wasn't a disc or something serious/major. I told her my weak back issues, and they tested my back and I didn't even move. When I got to my psoas muscles, I nearly hit the roof.
Once I started to loosen my psoas up, I'm fine and have been squatting again for about a year. Nearly back to my old weight.
So, I'm not saying that's the your problem, but if you haven't, maybe something you can check into.