Does anyone have a reference for adjusting a panic bar on an exit door?

It's a glass entry door, with a Jackson Exit Device (the long bar that
goes across the door, attached at each end to the door frame. You push
down on the bar to exit.).

If I push the bar to exit, sometimes the bottom "peg" doesn't retract
enough (or stay retracted), and it hits the threshold as the door closes.
Strangely enough, if I open the door using the outside keyed lock, the
"peg" does raise up high enough and the door will snick shut.

I tried the Jackson web site, but couldn't find any adjustment info.

--
charles