Red triangle, VSC, brake, and Hybrid System indicators

09 Prius w/ 89k miles, has has the 12v battery replaced a couple of years ago.

The problems started with the speedometer cluster never lighting up on the previous day at startup, but the next morning, to cluster lit up and ran fine. However later that morning, after going a few miles away, the Red triangle, VSC, brake, and Hybrid System warnings turned on. After these warning lights, engine was soon shut off the engine as well as any electrical forward motion. Turning it off then on, the engine would run for a few seconds then the warnings would trigger again. (I peeked at the 12v voltage, it it read 12 in accessory mode, and 14 when the motor was running...).

Towed it to the dealer to repair, and they've kept it for almost two days diagnosing it. At this point, the dealer says there are no codes to diagnose, and that it's now running fine for them. Their best guess was some bad fuel or rodents attacking wires causing an intermittent problem (that they now cant find...). I guess they're talking about kicking it back to me after running a last set of diagnostics. This doesn't make full sense to me with the range of warning lamps lit up, and it certainly doesn't feel very satisfactory. What do you think is going on here?