I'm sorry to trouble you. My link is about similar transmitters.
Making a guess here:
Could it be that the output is jumping around because that’s what the pressure of the fluid is doing? Many kinds of pumps can add pressure variations as they rotate or reciprocate, or whatever.
Maybe all that...
When we use the pressure transmitter to measure the flow of fluid, why doesn’t the output of the transmitter stop at a specific value?<a href="https://okmarts.com/transmitter/yamatake.html">Yamatake Transmitter</a>