There is a trouble shooting guide which covers these magnet
GUI reboots among other common problems:
hallaweb.jlab.org/experiment/HAPPEX/troubleshooting.html.
which is linked from the HOWTO:
hallaweb.jlab.org/experiment/HAPPEX/opmanual.html.
Now there have been problems getting to these web pages (unreliable
web service) which I'm trying to get CC to sort out. They work at
the moment (for me). In any case, I'll make sure we have up-to-date
hard copies in the counting room.