Merrychef 402S Repair commercial oven keeps restarting / won't start at Subway in San Jose, CA

The customer called us complaining that every time he would try turn on the oven, it would restart every few seconds. After our tech checked the oven and looked through the manual, he decided to try replacing the Logic PCB Assembly Version 3.0 SA260 и Display Assembly & Header Version 2.0 30Z1299, but it did not help, so he also replaced the Relay PCB Assembly 11K0004, after which the oven stopped turning on at all. The tech put all of the old parts back in, and, surprisingly, the oven started working and would not restart after a few seconds, which was extremely weird so the tech decided to run a couple of cycles to see how the machine would behave. He tried turning the oven on and off a few times, and it stopped working again, so he ended up installing just the new Relay PCB Assembly 11K0004 after which the oven started working perfectly. Also, the oven was intended for 240VAC, but it was only getting 208VAC which, as the customer explained, was caused by replacement of the components of the oven for the 208VAC about 6 years ago. In addition, the tech changed the 12.5VAC transformer to 208VAC since this transformed has been working on 240VA for the past 6 years. Finally the Subway customers were able to get their perfectly roasted subs.