It may be as simple a matter as spraying the connector rods with WD40 or PB Blaster. Follow the links from the lever to where the HST connects and spay all the linkages well. Of course, this is usually a "sticking" problem where the operator lets go, and the pedal doesn't, but it may be the same fix.
Other than that, I agree that you may need to adjust the pedal lie by changing the linkage position. John