DoorKip

Before I start, I should mention that while I wasn't looking the game updated to 1.1.1, so if there are residual issues that might be at fault. I tried the fixed dll that you provided and it seems to have fixed the problem, but for the sake of completeness I thought it wise to provide you with another simulation log so that you can verify that the changes you made are having the desired effect. I had the game create a fresh output log, and then had the game run a verbose simulation on the 17 part craft, and then created a new vessel of the same configuration as the one in the picture I posted earlier and ran a simulation on that. Here is the output log for those tests: https://www.dropbox.com/s/f076g5wni12wv9j/output_log%202.txt?dl=0 If you need me to test anything else out for you, just let me know.

Ah, sorry about that. If I have it right, this should be the right one: https://www.dropbox.com/s/pktzm0617y3nj3s/output_log.txt?dl=0

I was able to reproduce the decoupler problem with KSPI-E and IFS installed, and produce a verbose simulation log: https://www.dropbox.com/s/wbp8zn80g366cxg/KerbalEngineer.log?dl=0 A picture of the craft for reference: Also possibly related, If I change the level of liquid fuel or oxidizer in either tank, KER will alternate between reporting the mass of the craft with all of the liquids consumed or, an appropriate amount of residual liquid so far as I can tell.