I'm afraid that this is to some extent a feature of both pedals. The PF pedal input "auto-calibrates" by assuming that the highest pedal value it sees is 100% and the lowest is 0%. Sounds reasonable, eh ?
But, if you hit your pedal particularly hard, it can go above the usual "highest" value and establish a new 100% setting at the new point. What you see happens if you hit it hard once, and then not so hard thereafter – you'll have trouble getting to the new high value again, so will tend to see something a bit less than 100%.
When you replug the pedal, it resets the calibration and starts again, so your normal high point is 100%.
Some pedals can be adjusted so they hit a hard mechanical end stop before the full value is reached, meaning that you can't go above this position.
