On my PbPro this is caused by the lid sensor magnet being badly positioned. When I close the lid expecting that to trigger suspend, it will suspend too early as the lid closes, then un-suspend once it fully closes. Suspending manually first (via keystroke, for example) and then closing the lid solves that. I've read you can fix the sensor's position if you're willing to open the LCD-half of the laptop. The other issue I have is if you plug or unplug the power (via USB-C, at least, I haven't tested using the barrel plug) it causes the PbPro to resume even if the lid is closed, so I always make sure to plug it in first and avoid taking it out while it's suspended.
Barrel plug will do it too. It's an odd behavior, for sure.
I don't think I even realized it had a suspend sensor in the lid. I suspend mine via the power menu, wait for the green LED to go off, then close it. If you've got the proper suspend (deep sleep) stack working, it's very much a power sipper when asleep as well - I've had it asleep for a week (when I thought it was off), and still had plenty of battery when I woke it up.
