Sonar shutting off at speed.

I have a Lowrance hook reveal 5 split shot. I bought it new 3 years ago. No issues until this last trip.

While we were going across the lake at speed (16 ft pontoon boat, 17 mph) the device would just turn off. I powered it back up and it would stay on for a for minutes and shut off again. Once we got to our fishing spot and tied off, it would stay on with no issue. Cruising at trolling speed didn't cause any issue either. Only at higher speeds. Connections seemed good. The lake wasn't rough, so there wasn't any jarring causing it.

Any ideas?