My kitchen sink recently has stopped draining. We thought perhaps we had a block somewhere so we took the pipes off to replace them. No blocks were found and everything was replaced. Only to have the kitchen sink still not draining properly. We used a camera snake and found no blocks further below in any of the pipes. I noticed that while running water the p trap only fills up to a certain point and then the water starts flowing back into the kitchen sink and won't go down the waste trap. As you can see in the picture there is an air gap in part of the p trap. The water seemed to flow a lot better once we unscrewed the vent some. As soon as the vent was unscrewed some it flowed and the air gap filled up with water. Do we have a venting issue? The sink is my kitchen sink which is an island sink so running a vent to the roof isn't an option. Any suggestions would be greatly appreciated.

no picture ?

possibly a failed AAV, commonly referred to as Studor vent.

Get the best replacement vent the one that cost $20 not the one that costs $5.

Would be best to get a photo posted because likely there's a problem with the way it's plumbed.