First I'll say I'm surprised at what Ruger said about fixing the gun. Your first post said it was very dirty when you got it. Now that you have the slide off get some gun scrubber spray and saturate the parts in the ejector, sear area. Let it soak a few then if you have access to air compressor blow out a much as you can (wear safety glasses) if you don't have access to a compressor buy a can of compressed air and use that. It sounds like you might have some dirt stuck in there. If this is not the problem it could be (because you said it felt loose) either the ejector, ejector pin or the sear could be worn so it will not stay in place. These parts you can get from Ruger.
Do you have a manuel? if not you can down load it off of Rugers website. All I can do is guess without looking at the gun. Good luck I hope you can fix it.