The majority of the time a new thread goes from a question to new part solutions, some that can be resolution and likely some that are off the grid, all skipping the troubleshooting phase. The intent is to be helpful. I think it is important to read them as directional still requiring troubleshooting verification.

Based on my experience the first thing I do is check my work if I have just replaced a part and I am experiencing similar or the same symptoms again. In this case next step would be to monitor real time voltage and/or spikes at the cluster with lights radio and fan running and compare to realtime voltage at the alternator. That would put focus on the alternator and might have uncovered the loose nut.

We have to remember that input depends on how many are responding to our threads and we don't know if input has any credibility. So a variety of sources, like BMW techs, friends, etc. are always best practice before locking in on a course of action. Odds are much better that we take the right course of action with this process but there will be times the collective input is still off target or doesn't include something like the plastic screw.

I haven't heard of the loose nut cause but thanks to your update thread readers will be contributing that to others in the future.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas