This is coming from a programmer who routinely gets Catalyst units from alll different vendors.
Some vendors are great and will do a good reinstall of everything after shows, others... not too much.
Personally what I've started doing is whenever I have a show I open up the mac, make sure everything is well seated, no connectors in side broke or damaged.
then I'll give the HDD a good once over to make sure there isn't anything excessive installed on the machine that could create conflicts.