Yeah, I saw those disco’s recently and thought it was a great idea.
I found out about three years ago that the manifold bought wasn’t utilizing “backchecking” shutoff valves as this same thing described happened to me for the first time. Which made me think well what the heck happened here and when cleaning it then I found out these check valves were not as advertised. I bought mine around 2008 also. Maybe the companies involved have started to do the right thing and actually use check valves. I know it was far too late to return or other but I went into Midwest and showed then what was happening as their current inventory had the same ones. No offer to help a guy out, nothing they just said oh what do you do.
Well what I have done since then is I have posted FYI’s when posts like this come up just as a heads up for both mentioned issues. I thought I had the issue licked and vowed to simply shutoff any kegs when drafting growlers like this etc… I even had a large dayglo note hanging off the shutoffs to remind myself, which I took off about a year ago when cleaning the fridge. So the other day I drafted a growler and opened the fridge to turn the gas back on. OHHHHHH I was awful sore again as I had to clean the lines and manifold out as I forgot to shut off the other kegs during the OP.