So after going through the save file line by line and comparing it to my earlier working save file, it appears that the issue was in the FLIGHTSTATE section of the file. For each VESSEL, where ever the following three lines of code appeared in the original:
modMass = 0
moduleVariantName =
moduleCargoStackableQuantity = 1
they looked like this in the edited file:
modMass = 0, UNKNOWN
moduleVariantName = , UNKNOWN
moduleCargoStackableQuantity = 1, UNKNOWN
I'm not exactly sure why that was added, when all my other save files seemed to figure out those lines fine, but it was an easy fix to find and replace/remove all instances of ", UNKNOWN".
This seems to have fixed my save file; it can now be loaded in 1.11.0
Just posting this here in case anyone else encounters this issue.
