Not too unusual to see shells not being ejected. The USH's are great guns offered at a great price. I guess where they saved some $ in manufacturing was in assembly. Small bits of machined metal have been found in some USH's in the ejector area as well as some ejector's that are just a little too fat.

I have taken care of all of my USH's ejectors.

Unfortunately this IS common - fortunately the fix is easy.

Just spray cleaning without disassembly is not the answer. You have to take it apart.

Drive the pin out that retains the ejector. Be careful as it is obviously spring loaded. Make sure you don't loose the spring.

Once apart clean it all out with a good solvent and the ejector, too. LOOK INTO THERE WITH A LIGHT AND MAKE SURE THERE IS NOTHING LEFT IN THERE. I have a bunch of USHs and they have all been cleaned out. None acted up and needed it but when I heard of the issue I did it as preventative. I recommend laying the ejector on a fine flat file or maybe even a sharpening stone and working both sides about 40-50 reps to assure it is plenty smooth before reassembly. Once the solvent is totally evaporated and all the parts are 100% dry, coat the spring with a thin film of light gun oil (rust preventative) and assemble with just the slighest bit of light gun oil on the ejector. Oil from the spring will keep things sufficiently lubed for years to come.

If you put a BB under the spring it will increase the pop of the ejector (alot).