Front Squat - Technique Fix/Issues

So lately I have been having issues with my front squat. I typically using Olympic shoes and use straps around the bar to assist with my elbows up. However, as the weight gets heavier I notice at the end of every the weight on the left side of the bar drifts slowly off the bar from its original placement. I dont necessarily feel a difference when coming up but I am assuming this may be a left shoulder mobility issue maybe or an upright issue, i dont know?

Other concerns and confusion I am having is whether I should retract my shoulder blades which helps with a big chest or protract my shoulders and flare my lats to keep tightness?

I tend to go ATG on front squats but lately been having some anterior pelvic tilt at the bottom and slightly rounding my back including upper upon coming from the bottom of the hole

Do you guys have any suggestions to help with these issues?

Thanks,

Mike