Fluval x2 keeps pulling air

Not sure but my new fx2 is continuing to pull air in from somewhere. I’ve tightened everything as tight as I can get it, took the lid off and used silicone lubricant on the o ring. Made sure all the rubber connectors are below water level. Also made the motor box was tight as well. I’m not sure what else to do. I can hear the air inside the canister and the past two days it’s been pouring out bubbles until I reset it, then it’ll be fine for a few hours until it happens again.