Hi, so as someone else commented before, I have mass problems too (I'm talking about ksp of course! ).
It's either a miscalculation in the VAB that doesn't allow me to launch/build, or a miscalculation at the launchpad or during other moments that locks the avionics and spoils my mission. This makes building a craft near the tonnage limit or avionics limit very uncomfortable...
For example I'm now building a moon lander with 1.7t avionics and I wanna put as much fuel in it as I can: KER, Mechjeb all say it's 1.696t. The VAB shows 1.9t. When I launch it, avionics are locked because the mass is said to be 2.696t...
I usually manage to identify the faulty part that alters the mass count: I've had this happen because of parachutes (realchute), because of wings (proc wings), because of fairings (proc fairings), because of srb (you can guess) and because of fuels (realfuels). Sadly there isn't always a workaround: sometime deleting the part and recreating it fixes the mass count for the vab (I have to do this everytime i reload the craft), allowing me to launch. Sometime deleting all fuel and refueling at launchpad fixes the avionics limit. As for parachutes there is no fix: the vab part list says the cone chute is 0.2t. I add it to my lander, go to action group and adjust realchute settings, now the parachute weights 16kg. But of couse the VAB mass count sees it still as 200kg.
I think this should be a major bug to focus on. It really is game-breaking.
One question: as for physics calculation (twr, acceleration etc) is the mass read correctly? Or do my rockets lose actual deltav because of this bug?
Sorry for the long post and bad english.
tl;dr Wrong mass count, many mods involved. Really annoying.