Nothing holds that side in (inside the front housing). It slips in, and then held in place once the housing is bolted down, or you reinstall your strut back on the control arm (depending on which way you removed it. Either is fine)
I’m willing to but you have a broken top mount on your front housing. It’s an aluminium flange with 2 bolts that is prone to cracking. Under heavy torque (usually reverse+4 low) the housing wants to move up/twist and it will break. Once it’s broken this same stress will cause it move around and your CV can pop out, you may also hear the driveshaft rubbing.
I’m willing to but you have a broken top mount on your front housing. It’s an aluminium flange with 2 bolts that is prone to cracking. Under heavy torque (usually reverse+4 low) the housing wants to move up/twist and it will break. Once it’s broken this same stress will cause it move around and your CV can pop out, you may also hear the driveshaft rubbing.