Sounds like air is getting into the negative spring and not equalising. Can you pull them up to full travel and have them stay there? Or do they suck back down again?
Try letting all the air out. Remove the valve core and sharply extend the fork a few times. It may make a big sucking noise and extend. Suggesting the air was stuck in the negative.
If that works it could be caused by a damaged oring, damaged air spring leg shaft or scratched internal of stanchion. Or even just too much grease blocking the port inside.
Either way. Probably another job for the warranty department. But might give you an idea.