I'm hoping this is in the right place. I can't seem to find any other help place for asking about pre-existing robots...

I have a Bandai BN-1. I bought it used and it had a broken gear in its right leg (missing a couple teeth, I will fix it eventually). I didn't use the robot much, but it worked. I sold it to a friend and after a while of being off, she couldn't get it to charge. She sold it back to me and I managed to reset it successfully so it would charge. But now, when I try to turn it on, one eye says "E" and the other "R", so I'm assuming this is "error." I don't know why. It would at least turn on previously for me, so I don't think it's the leg.

Any ideas? I don't know how to fix this sort of issue other than general troubleshooting.