Why is my bobbin case jumping about?

I have an E&R classic model KPN400. It has a bobbin case which you put in the side. It has started jumping about as I'm trying to sew meaning the horn comes out the slot for it and my machine stops working. I've taken it all apart and cleaned/oiled it and there is no visible damage.

Also, now when I'm trying to start sewing my needle thread is not picking up the bobbin thread (even when I hold the bobbin case in place) and the needle is sometimes catching on the bobbin case when I'm trying to do it. It's all threaded correctly and the needle isn't damaged etc.

Does anyone have any suggestions as to what is causing this and what I can do to fix it please?

Thank you.