I just realised that when we give names to parts in Geometry section, e.g. Bolt 1 in the screen shots below, that is reassigned to a different part in FE Model section. Please see Screenshot below.
I have tried it in 1.4.0 dev version, and for me, it works. Did you do anything special with the parts before renaming them? It would help if you could recreate the issue and report the steps that lead to it.
Thanks for the video. That is really strange. Is it possible to share the geometry with me? Or the pmx file after the meshing? Or can I use the file from the topic Bolt Preload for Piping connection - #16 by datsnl?
I have fixed the problem. It appeared only for compound parts having more than 10 sub-parts. I have fixed the problem and updated the v1.4.0 dev PrePoMax version. Please confirm that it works.