I know that feeling Doc, Got the itch to play with the Works cocker, so I had the gear bag at the shop. Start my changing all the batteries in the Halos (3), Making sure all barrels were clean (8), Gassed up and chrono'ed the guns (4) Works Cocker, Ion, hAir Mag, DM3, Fill Tanks (4) 2 45/4500 and 2 68/4500.
Everything was in tested working order.
Next morning at the field grab the cocker, and some how the ram was bent to the point of not working, ok grab the Ion, at this point I had owned it since new and I have NEVER played a game with it, it had been my loaner gun to the kids on the team w/o a back up. Gas it up and the stock reg gives up the ghost spiking the gauge and popping a hose. Grab the DM3 and it sounds like someone is stepping on frogs and it not happy with something ( wasn't doing that the night before ) So go back to old reliable and Grab the hAir, not a hick up out of it, shot 2 cases of paint, played the full day and only issues were 2 of my 4 tanks were out of hydro (woopsie).
As a guy that works in a shop, I kinda pride myself on my kit always working, I had a serious complex that day about my stuff and the fact that I had to goto my 4th gun.
As to your flatline fill nipple, those were spec'ed by Tom for 6k pressures as I recall and are very tight on tolerances, you will typically find that cheaper ( 4 ball ) couplers have more issues with them than the better 6 ball fosters. For when I was playing tournaments I had made a coupler with a god foster on end and a cheap nipple on the other to avoid issues.