There has been various people over time who have experienced spiking with their pedals on G25 & G27's, myself included.
It has also been hard to find replacements however I located these replacements.https://www.digikey.com.au/product-detail/en/cts-electrocomponents/450D103F7/450D103-6-ND/183274
I grabbed three for around $17 plus delivery from their Aus web site.
I fitted them and found the following minor issues.
The main shaft is slightly shorter but has no effect on installation.
The small loops on the electrical connectors need to be snipped off to allow normal connection.
The hole in the metal pedal body that you slide the shaft through is around 1mm to small, so a quick drill to enlarge fixes that.
Once installed, I found they have a different range of motion to the originals. You need to go into Options | Controls in AC and adjust the min and max values for the pedal (see Pic for my Throttle).
With this done it operates completely fine.
Update: I reset the pedals (usb in/out or reload profile in AC) and range issue was gone!
Upshot is a brand new potentiometer for minimal spend that works correctly after a few modifications.