I have tried to design a very small Spaceprobe, when i saw that the Mass of it more than doubled when i tested it inflight. I have then experimented a bit, a the weight bonus is added to every Command part ingame inflight (+49kg). I am using a RSS/RP1 install in KSP 1.3.1 (via CKAN) . I have tried to trace it down to to a Mod, it should be somewhere in the RP1/Realism Overhaul in their dependencies. Ckan Modlist is linked there: https://www.dropbox.com/s/6uxbrf2xp7xnprw/RSS49KGBug.ckan?dl=0 . This bug, which is obviously greatly hurting my ability to make small Stages and Probes, can easly reproduced by just launching anything with a command unit.
Thank you for your time
Edit: Picturesfolder: https://www.dropbox.com/sh/ijnxcjj9ore8r5m/AABHczmZT6-_xt6OX8j0e3TJa?dl=0
Edit2: Logfile: https://www.dropbox.com/s/zhddilm6d2abgqt/output_log.txt?dl=0
Craftfile1: https://www.dropbox.com/s/a6zjwmpx2cp9jw1/Test 1.craft?dl=0
Craftfile2: https://www.dropbox.com/s/4cq8kjnr1il5db7/Test 2.craft?dl=0