I don't have a manual and mods.dk doesn't have one
listed so I know how to perform a reset on the rig

Ian-

I don't recall that model. Is it possible the TS-480S is a typo? Might it be
a 430 or 680?

Either way, your description of the problem makes me think of a CPU that is
hung-up. You might try exercising a master reset, but you might need the
manual to do that. Often a reset is done by holding down a particular button
or combination of buttons while turning on the power.

Another thought is that your CMOS memory battery is almost dead, but not quite!

73, Fred, K4DII