Any JR Guru's Out There?
You should probably just send it in to Horizon for repair, usually $15 to $50 at worst case.
These radios' computers are default in Mode 1 because most of the world is Mode 1. There are jumpers somewhere in the radio of American 631's to tell it's computer to be Mode 2.
At some point in the radio's life, the radio may have been connected to a "wrong polarity" charger, or it may have had a battery lead issue. This event locked up it's computer and may have done other damage.
Unfortunately, damage may have occured to the main board or the RF board that only Horizon can fix right. The 3V lithium may have drained due to the lockup, etc. The radio's tuning and output may have been thrown out of whack by damage to the RF board. This will result in eventual failure, weak output, and crashes.
I would strongly reccomend sending it in to Horizon to get fixed and looked over.