what or why does the serial # order affect things?
I'm not exactly sure as to the what or the why. All I know is that PRESONUS tech support has stated that this is how it needs to be MANY times in MANY threads. As they designed these units I'm sure there is a technical reason but I neither know nor, frankly, care what it might be. I'm willing to accept the manufacturer's advice....when it works....as it does in this case.
its just strange how the ac or dc supply is affecting the sync.
No, not at all. Though many devices can run standalone on either ac or dc, ( IF their internal
components are designed to do so), trying to sync two units together with one on ac and one
on dc is the electronic equivalent of trying to force a square peg in a round hole. Frankly, I'd be REALLY surprised if they DID maintain sync. I'm sure things will work better with the new AC supply....try not to blow this one up.....LOL!!
That being said we can help you better now and in the future with a bit more info......if you will post your system specs in your signature, (see my sig), we will be better able to troubleshoot your problems. Without knowing what type of pc you're running, what OS you're using, what DAW etc....we often can't recommend a "simple fix"
If you have not already done so please READ THE MANUAL!