It sounds like the OP did not replace those. I did not see any mention of them anywhere here.
When I did suspension work on my '01, soon after getting it, prompted by excessive, uncorrectable rear camber and rear tire wear, I was pretty careful about not replacing things unnecessarily.
On my car, those carrier-arm ball joints (BTW, they're called ball joints, but there is no ball, they seem closer to what I would call bushings) were perhaps the only items that NEEDED to be replaced. I did replace many other things, "once I was in there" (integral links, since you R+R them to get to the ball joints; and then, hey, since you're paying for an alignment, may as well replace anything that seems less than perfect on the front - that's what I did).
I used Lemfoerder 33-32-6-767-748, "Rear Ball Joint", superseded from 33 32 1 095 631. Same both left and right.
I took a quick look at that video - looks good. He gets to the actual pressing out of the ball joints around 7 minutes in. Don't be fooled.
Doing that without the right tool can be somewhere between frustrating and impossible. I used local-rented general purpose tools, and it took a lot of work/experimentation/fabrication/swearing to get them to work. The BMW-specific tool for this job has (I think) a special cutout in one of the cylindrical pieces, allowing it to sit properly in place. This minor feature (as I've heard, and can fully believe) turns the almost-impossible into easy.
This particular job is very important on these cars, and you'll find a lot of references on this forum.