The sliding case feeder on my Lee APP would often bind causing the spring link which moves it to bow. This seemed to happen more often when things got a bit dirty or when using the press for "bulge busting".. Very aggravating and slowed things way down.
I cut a piece of 3/32" rod to about 3.5 " long and inserted that inside the spring link. Problem solved. The case slider moves much more positively with some of the spring link flexibility removed by the internal rod.
Hope that "fix" might help other APP users as well.