A jackshaft opener on a rolling steel door is not a DIY afternoon project. The torsion on a commercial door built after 1999 to hold a wider bay is a different animal than a residential double door - the spring is wound tighter, the drum is heavier, and the operator is often hardwired into a building's electrical panel rather than plugged into an outlet. If a cable frays or a spring lets go on one of these, the door can drop fast and hard, and there's no safe way to hand-crank it back up without the right winding bars and a second set of hands who knows the sequence.
What you can do yourself: keep the track clean, check that the photo-eye brackets haven't been knocked out of alignment by a forklift or a pallet jack, and listen for a grinding or clicking sound from the operator before it fails outright rather than after. Past that, call it in. We'd rather talk you through a five-minute fix over the phone than have you climb a ladder on a 200-pound door section.