I have my sons 45/70 barrel here and I just played with the ejector. It is completely contained with on the welded on pivot lug. On this one I can press it in by hand and using a hard piece of plastic trip the ejection by pressing on the rear part of the the trip mechanism. The extractor then kicks out smartly. If that lug is full of dried oil I guess it could be cleaned out with solvent and compressed air. There are at least 2 healthy springs in there might be hard to reassemble if it is necessary to take it apart. If the ejector mechanism is working properly then something about the chamber is the next suspect. Dirt or physical damage?
OK, I did one last experiment. After pushing the ejector in, I can pull down on the 2 ends of the forward roll pin and make it trip and eject.