Has anyone had problems with their RFC-E foot control producing less than the set peak welding amperage?

I bought my Miller Foot Control model RFC-E to use with a Maxstar 91 years ago, but rarely used it, replacing it with an RFCS-14HD because I liked the heel stop on the newer pedal. I brought the RFC-E out of storage and attached it to my Miller Dynasty 200 DX recently and find I can not produce the top amperage set when welding; for example if I set the peak amperage to 55 amps, I can produce only about 28 amps while welding with the pedal floored.

After several frustrating runs, I measured the resistance of my old trusty RFC-14, the RFCS-14HD, and the RFC-E. The RFC-14 and RFCS-14HD produce a resistance range of 0 to 1K ohms while the RFC-E produces 0 to about 700 ohms. I took the RFC-E apart and adjusted its internal gear on the potentiometer by a tooth then put it back together and tried it again. Now the arc comes on too hot, but does go all the way to full set amperage.

The RFC-E's trouble appears to be a design problem. The full travel of the pedal does not rotate the potentiometer through its full 0-1000 ohm range.

Is anyone aware of a recall on this product or a repair kit that corrects this problem? The owner's manual does not show internal parts. Elsewhere on the web I found a post saying this model foot control was OEM'ed by Miller from Linemaster Inc. Any truth in that?