Control.com - Nerds in Control

We have 4 GE frame 9E machines controlled by speedtronic Mark-IV. We have observed that during running of GT on gas fuel intervalve gas pressure (FPG1) transmitter for T computer shows higher value as compared to R and S. this leads to mismatch in servo currents wherein T always issues negative current.

There are a few related observations:
- Intervalve pressure transmitter for T comes first in the three-way valve header for the three intervalve gas pressure transmitters.
- All three transmitters are calibrated simultaneously in their mounting manifold by applying pressure at inlet of the manifold.
- We adjusted T transmitter a couple of times and then installed a new transmitter.
- LVDTs are calibrated properly over the complete stroke of the valve and the two LVDT feedbacks match to each other.

My question is, when LVDT feedback and intervalve transmitter values match perfectly during offline condition, why does the transmitter for T computer give a higher value during turbine running condition?