they also suggested this may have something to do with their versions being modded.
this is possible if you have modded galaxy models
So I guess my question is what influences whether or not a planet is the same across different computers?
Normally it should be the same across all computers, but it might be different due to modded galaxy models or bugs.
And procedural object locations of older versions of Space Engine can't be found in the current version. You can only go to locations someone else found in the exact same version of Space Engine.