Modular RCS does not have a consistent weight after changing propellants.
Steps to reproduce:
- Add a Modular RCS
- Check the mass (0.006t)
- Change to HTP. The tech level is increased and the mass changes to (0.017t)
- Change back to Nitrogen, and the mass remains 0.017t instead of 0.006t expected
Also, if you add the Modular RCS, Nitrogen, upgrade the tech level and downgrade it back, the mass is not consistent either. Does not return to the original mass.
In the same manner, if you add a Modular RCS, then change it to HTP (it auto increases the tech level and mass), and then you copy it. The copied one is lighter, because even though is HTP, it begins with Nitrogen lvl 1 mass.
One example:

Another video example https://discord.com/channels/319857228905447436/331813459417235457/1387536559204597791