^^^ If you expose the rx to a lot of dirt, dirt can find its way under the pcb in the base of the rx and cause all sorts of probs. Worth taking apart to see.

One of the guys here that seems to work with Futaba mentioned that rxs do go bad due to vibrations and shock from hard landings and etc. Maybe its just gone bad.

Futaba used to repar rx for a very reasonable flat fee. It took a while being the downside. I used to buy used 113ips and got a few bad ones and just send them in for repair. I don't know if they still do this and if so how much, but you could check and see if its an option top consider. Prob just emailing them.