Agree with what you say except on intercooling .
For example a mycom compound uses only oil to cool interstage as well as some Grasso's pump directly from booster staight into high side suction .
On this plant he also has a side load from economizer suction .

If we know where pressure drop is when Cryo99 get back it may narrow it down as well .
He says there is no purge point between condenser outlet and liquid reciever , so he might be taking reading at HP reciever ?