2019 Yamaha 200hp - Main/PTT 20amp fuse intermittently blows

I have two 2019 Yamaha 200HP (inline 4) motors on my 2004 GW Gulfstream. It has about 120 hours. During last year's season, it has developed an annoying issue to blow the Main/PTT 20amp fuse intermittently. When is blows, the engine shuts down and the guage on the dash does as well. It is the port (left-hand) motor. The mechanic thought they had 'fixed', found a loose connection on the engine. Took it out, same problem again. It is at the mechanic again, and they found different loose connections (these are bolt/connections not plugs) at the engine (send me a video where). The two he found loose (in video) was the one without a cap (red dot on it) and the one directly to the right. Not loose that you can see it, but but if he touched the cable it moved). They are going to review all 12V connections. I am wondering if there may be another problem, like a short that has chafed in the circuit between the engine and the dashboard. Only thinking that since the motor is relatively new, but the wiring from the engine to the dash are original (as far as I can tell). Any ideas where to start troubleshooing if the loose connection does clear the issue?
Thanks in advance.
Len

Per mechanic, the main engine harness has a bad diode (or something like that) and that it will be replace by warranty. Bummer is the harness is backordered and currently unavailable until end of July. In the meantime, I will be replacing the harnesses that go from each engine to the binnacle/helm and possibly replacing the binnacle itself. All parts are 18 years old. I'm thinking doing this as preventative measures.

Slight update. Apparently they found a bad 'diode' in the engine harness. It took a while to get the part, but it was installed and got my boat back yesterday. I will run it Sunday with my fingers crossed. In addition to the warranty harness replacement, I installed new (almost 20 year old) rigging harness (from helm to binnicle) and a new binnicle. I wanted to start out with fresh wiring and especially new connectors. Hopefully I'll be able to post a successfully test run and head over to Catalina Island.

Had a good trip from to Catalina Sunday. A little frustration at the launch ramp. Port motor started right up, that's the one that has the problems. Starboard wouldn't start, not even turn over. After cussing on it, and that didn't fix it, I took truck/boat to back end of launch area. Worked on it for almost 3 hours before I figured out one fo the two paraled batteries connections wasn't connected. My guess is that the mechanic had to take the battery set-up apart to get the new rigging harness and didn't but it back. Between that and me cleaning up all electrical connections, it was good to go. By then the wind/chop picked up so it was a good test. Had to adjuct friction of throttles on the water, which worked out okay as well. Hope the intermittent issue has been finally solved.