Buck-boost transformer

The output voltages, measured the same way are 266/327/227.

By "output" I assume you mean the high volt side. Check the transformer nameplate. I would guess that the high side is connected in a delta configuration and is isolated from ground; therefore voltage measurements with respect to ground are meaningless. You did say that line voltages on the high side measured normal at 480V, right?

As for the low side current measurements; I wonder is the "130" a typo? If not a typo, this would indicate a gross load imbalance. But you say the high side currents are within 10A of each other. The math doesn't add up here. If that is the case, then the low side currents would be within, roughly, 25A of each other. Maybe someone with more experience than I have can explain it.

Ok, I understand why the 480 side voltages are irrelevant. It is a Delta configuration. The 130 is not a typo.

We had a similar problem with a Trane 20 ton A/C unit. After much research found the problem to be undersized. After replacing with transformers twice the size we have had no problems since.

Steve