OK, so I have a converted chest freezer with 2 ventmatic faucets connected with 3/16 beer line 6ft long at 12-13psi. Everything is inside the kegerator and the lines are elevated above the kegs. No leaks. First keg no problems. After that no matter which keg I pour from I have to fill a glass half way with foam dump it and then I can pour a nice glass. It's fine if I pour more than one at a time but if I walk away for 30 minutes(if that) and pour a new glass same thing happens. I have tried just about eveything I can think of. Suggestions?