Hi RANGER1,
an interesting problem, I have seen those Mycom compounded screws, but never really worked on them.
Oil temp is critical, Frick use Amot three port control vavs., and I have had a few of them play-up with age, which in turn put a larger load on condenser. It will be interesting where the HP pressure is being read from, the set or the condenser, I am picking it is from the set, from where all control functions are from.
As you said earlier the current refrigerant will put extra load on condenser as well, add all and any other problems will ramp HP problem
Come back to us all Cryo99.