Undetectable leak?

[JuanKenobi]

So I have a keg of stout that has been on gas for 27 days at ~10psi (serving pressure) that is just not properly carbed. It is carbonated, but just barely, and not at all like a bitter that is on the same regulator. Yesterday I pulled the keg out (without disconnecting anything), and leak tested it with a spray bottle of starsan. I was very careful to make sure that I tested all the connections and gave it some time (like 10 minutes) to manifest any leaks. I couldn't see any.

I'm assuming that there must be a leak of some kind. The only weird thing is that I realized that I put the keg back together with the 'IN' and 'OUT' labels backwards, but I can't see any reason why that would matter.

Has anyone else had experience with a leak this minute? Or could there be some other factor that I'm overlooking?

 

[iaefebs]

What temperature you are carbonating at?

 

[JuanKenobi]

Fridge fluctuates between 37-40. I call it 40 for beersmith's sake. At any rate 10 - 11 psi gives me the best pour, so that's what I go with. I don't have a budget for secondary regulators, etc. to hit style volumes at the moment. I've never had this problem before.