Getting some strange behaviour with Modular Fuel Tanks. It's clearly present and functioning, but it can't be applied to any of the OPT parts.
KSP.log at the link below. https://drive.google.com/open?id=1sHAuLASGGNJ1Y0lom1kE_QcIjnWJs-kI
@Starwaster I don't have RealFuels installed.
Both the log and ConfigCache are too big for Pastebin.
https://drive.google.com/open?id=1nqmnxiw6pP-GfDAhaVaFTipboPPnEvBx
https://drive.google.com/open?id=1j1pGIHBxILY3Aq9xrXtr40UimBvmJvDL
Signal boost on this bug; I'm getting it too on 5.13.0 for 1.8.x, even while running only MFT and no other mods.
Whenever I reproduce, the logs start to look like this:
https://pastebin.com/mKd8XgTb