Paul, glad you found the problem & got your rifle back online.
Just as a precaution/preventative on my .25 carbine, I use Zerk fitting caps similar to these to keep trash out of the male Foster QD fitting, along with a dead head in the female QD on the fill whip. You may be able to get these at an auto parts store too. I like the ones with the attached ring to keep the cap from getting lost.
Those are the type that come on the Texan. For that price its a steal and too easy to use as they stay on the nipple during filling with the ring. I replaced those with the metal ones like below and havent had any issues with loss as the rubber ones can tend to tear. Theyre available in numerous colors and I use them exclusively now. With the right color, they accent the gun quite well. They are more expensive though.