Vintage Double Hose

I received my Kraken DHR in December last year. I've been able to get 6 dives on it so far, all within the last month and a half. I noticed at the end of my 6th dive when I closed the mouthpiece on the surface air was still bubbling out slightly while I was on my back. I'm 6 dives new to the DHR, never having had one in the past. What should I be looking for as a possible cause and a fix?

I think I would disassemble it, carefully clean it and lube the o rings. Put just enough silicone grease on the o rings to make them shiny. This will probably solve the problem

I posted a similar problem a couple days ago called "DSV Oring Problem" that no one has commented on yet. I believe it to be opperator failure. I use it several times every dive, and never re lubed it. The oring stretches when I open/close it, causing the oring to pop up and pinch in the gate?. I solved it for now by greasing the oring and entire area the oring slides against. Normaly I would just make the oring shiny, but the mouthpiece oring has a long way to slide on plastic that has gotten scuffed up prety good. Look in your mouth piece with a light and see if yours is coming out of the groove. I plan on cleaning and greasing mine more often.