One thing I use to see a lot when I wrenched fulltime, is the brake shoes mixed up.
Both primary shoes on one side and the secondary shoes on the other.
Or one side you would see the the primary shoe on the front, and the secondary on the back, while the other side has correctly installed shoes.
The primary shoe, (the one with more brake lining surface area) goes to the rear. And the secondary shoe(one with less lining material) going to the front is the correct installation.
I'd check or replace the other wheel Cyl. too. make sure the pistons in it move freely in and out of Cylinder.
1991 525i M50 5 Sp.
N.California
America is all about speed. Hot, nasty, badass speed. -Eleanor Roosevelt