First I've ever had to repair, melted flash sync safety switch in OM-1 .  These close as the mirror goes up, then as first curtain clears the aperture, main contact closes (they may also be fried).  Without a safety switch, flash would fire as it was slipped into and out of hot shoe, and would fire as the shutter was wound.

 

Photographed with E-500,  50mm f2 OM Macro lens, FL-36 Flash