Make sure that you've calibrated the pedals in Windows first and then in Aces High, you'll need to calibrate the pedals twice. Go to the controllers section where you assign the axis and highlight the pedals and select the "calibrate axis" button and follow the onscreen instructions to calibrate the axis. After you've done that, go to the "calibrate controllers" section in the clipboard and follow the onscreen instructions to calibrate all of your controllers.
If the pedals still spike and adjusting the deadbands don't work, if you're not using one, try connecting the pedals to a powered USB port and see if the spiking continues. If it does, then most likely it is the potentiometer going back and needs to be replaced. Usually, it's an easy thing to do but with the CH pedals it can be difficult because of how the pedals are designed and putting them back together can be a real pain in the ass. I think CH Hangar has a walkthrough on how to replace the pots.
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