I'm using HD500X with Line6 EX-1 pedal and I have this problem. Internal pedal of HD500X works without any problem, but external EX-1 pedal doesn't have that perfect "tracking" and I get 100% value when I'm let's say in 85% if compared to internal pedal and I get 0% value when I'm in 10% if compared to internal pedal. (I hope I explain it so it's possible to understand, I'm not native speaker).
I don't see way how to calibrate external pedal in same way as internal pedal.
Can anyone confirm this behaviour of EX-1 pedal so I know there isn't any problem with my HD500X or EX-1?