OK, ELIS. More questions:-

Is this a new piece of equipment, recently commissioned ... or something old, and rarely used?

Is it excessively humid in the theatre?

Have you checked out the kit with your Electrical Safety Tester?

If there is a fault, take a close look at leads and cables (especially those that may have been "run over" by wheeled equipment) ... then take a look at the power supply unit (big fat capacitors?). smile

If you don't inspect ... don't expect.