Skimmer help

[Animal-Chin]

I just bought a Vertex Alpha 170 skimmer used. It has the big external red dragon pump, the thing is a beast.

I've set it up in 10 inches of sump water per the instructions.

Been running 4 days so seems broken in.

Last night the water level in the skimmer started going nuts. It'd be skimming normal, the water level was only a small way up the cup neck, making froth, then all of a sudden the skimmer would go nuts and overflow. I'd have to open the gate fully and decrease the air fully just to get the water level back in the neck.......5 minutes later the water would be way down in the body and I'd have to ramp it all up again..........hour later super overflow.........

Any experience with this? Am I getting some sort of air lock somewhere in the lines or something? By the end of the night it calmed down and skimmed all night but it took me hours to get this thing to just work properly. Is this common? I've never had a super skimmer like this....