"Module Stager" Log Spam

[Brigadier]

KSP 1.3.0, Win10

Recently, I'm seeing tens of thousands of "Module Stager threw during OnFixedUpdate" NREs.

Quote

Module Stager threw during OnFixedUpdate: System.NullReferenceException: Object reference not set to an instance of an object
  at Lib.Stager.OnFixedUpdate () [0x00000] in <filename unknown>:0
  at Part.ModulesOnFixedUpdate () [0x00000] in <filename unknown>:0

I've never seen these before and I have added a couple of mods recently (Smart Parts, Precise Maneuver, NavHUD).  I've search the entire forum for any reference to "Module Stager" but can't find anything.  Does anybody have any suggestions where to turn to identify the mod responsible?

Without any proof on my part, they seem to associated with my using a Tarsier space scope, but before I pounce on the that thread, I thought I'd ask a more generic question.

Full log here.