Mesa 7I96s - 5 AXIS

Really don't see what could be different between configurations that affect basic communications.

unless there is some marginal power issue (does the 7I96S reset when starting the 5 axis configuration?)
Or maybe a memory fault of some kind in the PC, the reported error really has nothing to do with the number
of axis.

And as I said, your 5 axis hal/ini files work fine here with a 7I96S

A pncconf created configuration might be worth a try, just to see if a quite different
5 axis configuration changes the symptoms.