I have modded the KerbalCrewMass value in Physics.cfg (as many have). In the latest release of KER (1.1.5.7) adding crew to a ship in the VAB sends all the KER values haywire. It worked more or less fine before.

Yea looking at this is on my to-do list, there was a bug in that feature a couple versions ago I had to make a workaround for. Maybe squad fixed it and now my workaround is inappropriate.

I observed that the dry mass is calculated in a weird way by the most recent version of KER.

If the part contains crew (e.g. pod) the mass adjustment is made by adding the vessel crew mass to the part mass. So, Mk1-3 pod weighting 3700 kg (empty) + 1 Kerbal (100 kg) = 3800 kg. This is OK.

But if the other parts contain no crew (e.g engine, tank, parachute, decoupler, heat sheild, etc), the crew mass is removed from each single one of them (very BAD).

So if you get a vessel with 6 parts (including one pod) and one crew member, the 100 kg crew mass is added one time (in the pod) then substracted 5 times giving a net 400 kg mass loss when comparing to the stock mass calculator. So it also messes TWR and Delta-V calculations in KER.

And if you middle-click on any part in VAB, the popup will show erroneous mass for the most part of them (if you get a parachute weighting 200 kg, and have three crew members, the parachute is calculated at -100 kg...