2004 Mercruiser 5.0 MPI "Engine Data Bus" Error

Hey there. We have a 2004 SeaRay SunDeck 220 and starting last year (and continuing now into this year) we've been stalling out at idle-level RPMs with the error "Engine Data Bus". Last year, it seemed to only happen after the boat had been underway for hours and as we were slowly taxiing it back into the slip. Didn't seem to happen unless the boat was in gear with as little throttle as possible. Engine started back up but if kept at that low of RPM, it would cut out within 10 seconds or so. This year, we have the boat in a floating lift, and I just lowered it into the water enough to submerge, and tried to start it. Same thing happens now, and pretty consistently, without having to even put it in gear.

We had SeaRay and another shop come out last year and spent over a grand having them repeatedly try to reproduce it but they were never able to and didn't seem to have a clue what could be wrong. On the bright side, if it's happening consistently (we'll see if it happens tomorrow) it should be easier to diagnose, but does anybody have any ideas as to the top three or four things to check? I understand from elsewhere in this forum that it's like a bad cable somewhere, but anything more specific than that or other things to check?

Thanks much. Engine info:

Serial #: 0M658186
Engine Model #: 4-M42037RS
Engine Model name: Mercruiser 5.0 MPI

Here is video of me trying to start it today, by the way: https://drive.google.com/file/d/1PKrMIgDg4cOLB7F798G-wLq46b9YdEHO/view?usp=sharing