You may be already doing this, but are you running the panels through a powered USB hub? They are very power hungry and ordinary hubs drawing power from the motherboard simply will not be able to cope, especially if you disable USB power saving settings.
I had similar problems at first with my three panels until I used a 13A mains powered hub.
Re: SPAD. It’s a bit of a steep learning curve, but indispensable once you get used to it. Connex is Ulrich, the developer of SPAD.