Unconsistent fuel amount and craft mass

2nd EDIT: i've found the cause. If you have a part with the command module modifier instead of a true command module (chip or cabin) then the game struggles to understand how the mass is changing

As you can see in the screenshots the group has 0kg fuel left but the tank has 100% it's capacity full

EDIT: This issue is partially fixed. Now the fuel flows as it should and the TWR changes but the displayed fuel percentage in the tank is fixed to 100% as well as the displayed craft mass, even though the real mass does change.

The problem fixed was that the fuel had to go through a tank that had the fuel tank modifier deleted, so it seems that the fuel line was broken there.