when i test drove my bus, the gauges weren’t working at first, then suddenly they kicked in but they were doing the same thing. the instrument cluster was reset and it’s been fine so far, although with my vehicle luck it will probably come back lol. my instrument cluster is actually going out in my car too, a lot of times i lose my gauges but sometimes it’s like they’ll get stuck on like 60 mph and high rpms (no engine response thankfully this is all gauges), so i’ll be going down the highway reading at 140 mph LOL. usually it resets when i turn the car off but sometimes it doesn’t.

i HAVE had the issue disappear for a bit when disconnecting and reconnecting the battery to see if it goes away- if it does, drive for a bit and see if it comes back. at the very least it might help your mechanic rule something out when you do get to them.