Strangely behaving 16c

[Taco Sundae]

Howdy all. I just picked a 16c up off of ebay. The problem is that it does not behave as I would expect. For example any multiplication seems to have the last 4 bits masked off of the result. So 15 3 * produces 32 instead of 45. Every product have tried has had this same peculiar defect.

I have tried a reset with [-] + [on] as well as shorting the battery terminals but the issue persists. I am new to the 16c so I suppose there could be some masking mode that is turned on, but a skim of the manual has provided no clues.

Another issue is that I cant seem to run programs. even when entered from the manual keystroke for keystroke I just get a error 4 every time.

A couple of things concern me about this purchase. One, the unit is in shockingly good physical condition. Two, the keys feel slightly mushier than I would have expected especially the enter key. The other keys are close enough to the hp keys I am used to (hp 48) that I would be satisfied, but the enter key feels awful. Very stiff with no real snap to it. Are counterfeit voyagers a thing? Other than those two concerns and the odd behavior everything looks legit to my admittedly untrained eye.

Any help would be appreciated