I've now done a more detailed examination of this behaviour and conclude that, during flight, there is a rate of memory allocation that is proportional to the total part count of all the on-rails vessels in the save.  This results in large and complex saves suffering significantly more with GC related stutter. This file contains the various saves the tests were run on.  They are all based on the "Platonic Stations" save which contains the top stage of a KerbalX in a ~200km orbit and four st
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