Hello there,
I have heard using a converter for a deans gun/Tamiya battery, (not the same ratio, but general comparison) is like running a waterfall through a funnel. Deans offers more surface area and thus better flow of electricity. Tamiya connectors constrict the flow, and can lead to the unnecessary heating up(resistance) of wires/batteries/connectors.
But enough about connectors. Other potential problems could be a loose connection somewhere, worn trigger contacts(more so if you use 11.1), loose motor brush/spring/tab, or a pinch or short in the wire. Or possibly some other mechanical part failure.
For semi auto (assuming you know how to change between fire modes), the internal "selector lever/bar" could be broken or stuck, or the cutoff lever OR spring could be detached or broken.
So for each issue your gun is having, it could be a couple different things. I myself am a repairs person, based a little more on the eastern side of the state (Troy/Royal Oak area), but I have been known to work with people, either meeting halfway(or otherwise arranged) or shipping. I'm sure the community can back me and agree that my prices are very reasonable, and that my work is quality.
Feel free to send me a message if you like. Glad to help if I can.