Individual vessels suddenly gain unplayable lag, but stop lagging on SOI change

[DAL59]

About every other mission I run into a lag spike where I only get 1/2 a second of movement every 5 seconds, if that.  This is similar to the common memory induced lag issue I and others have often had, but it is not fixed by Memgraph or Padheap, and only effects a single vessel at a time.  Restarting the game/computer has no effect, neither does quickloading or using the tracking station.  However, as soon as an affected vessel changes SOIs, the lag vanishes.  Some affected vessels had partcounts <10, so that isn't the problem.

[DAL59]

I am on an M1 Mac if that helps.