In my experience, that's how Meanwell power supplies are. Supposedly the noise goes away if you put a dummy load on the 5V line, but you'll never get a straight answer from anyone online as to how to go about that (don't ask me, nobody would tell me, either) because everyone assumes you'll kill yourself. These power supplies are not designed for powering modular synthesizers and can't really be relied on to be stable voltage sources. They're primarily intended to be used as 5V power supplies. You're paying for what you get. I used to have one in a small case and you could hear the pitch drift in the oscillators, they were never totally stable. I switched to an Endorphin.es 2hp power supply for that case and it cleared everything up.