There is a known design fault in the remote that is prone to breakage. Removing tbe battery stresses the existing fault and if it wasnt already broken, likely is now.

Some years ago i bought an upgraded remote that has had the soldering deficiency fixed. It was about fifty bucks,iirc. But to be honest, nowadays the remotes can be bought cheaply on fleabay for half that, in contrast to tbe ridiculous prices Mitsubishi wanted for them. I think they were asking at least 150 each when i queried tbem.

My suggestion is to pick up a couple and always have at least one spare remote tuned to your car, ready for use.

Cheers,