This I have noticed, not so much for DP, but simply for hard riding, I'd like to be able to stick it to a wall, push back against it, and it slip in on its own.
Also, this is a bit off topic, but I've noticed the suction base of the Akita is a bit small, as it won't quite support the hanging weight of it.
I get that, too. I can be riding it in a dry tub and it'll come off without even being knotted. So you're not alone in that problem.
That's why I got my Akita in firm but being so long I kind of wish it was softer so that it'd flex inside me easier.
My Akita has no suction problems at all. If pulling directly against it, it takes about 100lbs of force to get it to come off. Maybe the surface yours is getting stuck too isn't smooth enough or something?
I wish I had gotten mine in firm... I don't even notice the depth, so I don't think that'd be an issue for me.