If you've got a second power supply, even if it's underspecced for the time being, try connecting its DC legs to the busses in the new cab after you disconnect the Meanwell that's already there. Then just put in a few modules that appear to be the "usual suspects" here and see if the buzzing continues.
The more this goes on, the more suspicious I'm getting that it might actually be an issue with the filtering on a busboard. By checking these using the older (and obviously functional) P/S, you might be able to eliminate the Meanwell as a source of the noise if the buzzing happens on the other supply.