Either call in the UIC or U1's decision stands.

From Rule 10:
"B" is pretty clear. The PU overstepped his authority. For that matter, so did U3 in going to PU in the first place. My guess - these two were buds and U1 was the odd man out (just based on how everyone's actions were described here). "C" might give PU a one-legged stool to stand on by trying to argue that U3's call was reversed, but it wasn't - it was a separate call, not a reversal of the out/safe judgment.

The tournament UIC can step in, but not the PU. JMO. Many of you have far more experience than I in these kinds of situations...

As a UIC, I'm not going anywhere near the field until requested by a member of the crew, not a player, coach or parent. If I'm near the field at the time of the play, I will disappear because if noticed, the coaches are heading in my direction and that is not the way it works.

If I ever need to talk to a crew about something that cannot wait until after the game, I will take them some water between innings and have a very relaxed discussion with the crew. Of course, I will take them water anytime they need it, not just when there is an issue.

I can hear those Delaware umpires now. "Oh no, here comes Mike again. And he is carrying water. Wonder what we f-ed up this time. " :D