By the way, there’s an old “trick” for temporarily fixing gurgling (or full liquid flooding): turn the RTA upside down, suck it to your mouth, and blow into the airflow a few times, then wipe away what came out 
This can help you a bit with troubleshooting, because if it no longer gurgles until the next refill, then there might be an issue with the initial steps (e.g., cotton amount, because pressure pushes the liquid in when closing the top cap, but it holds vacuum afterwards, O-rings might be good etc.). If it returns after a few puffs, the problem is general (O-rings, cotton, or anything else…). I think