This is a bitter lesson to learn but...
a few years back I placed a post concerning the R&R of parts.
ESPECIALLY, lower body, brake, powertrain, suspension and steering parts.
Here's the short version....
Whenever replacing parts that are in contact with crud and water, it is cheaper (and in the long run easier!), to replace the parts along with new hardware.
So....if you going to do any work, when ordering the parts, order the associated hardware. Generally, it amounts to a few extra bucks but it will save you that in time and heartache.
In some cases, BMW stipulates that you NOT use the old hardware so, of course, you should order ANYTHING that they state should be replaced....
Don't be cheap!