This one has been around a while and is described in detail in Maguro’s Bug Hunt VI “Trains & Conjoined Behavior”
(I unfortunately can’t link to it, but it should be on top in a google search)
Basically, in the coop mission Oblivion Express, trains typically don’t receive the damage they should, instead trains only take damage from the train part receiving the highest damage in each damage tick, the rest is ignored.
It really hamstrings commanders who can’t easily focus damage on one train part.