I just bought a Ti-83 Plus Silver Edition and the arrow keys are double typing. Pressing the left button sometimes causes the cursor to move two spaces left instead of one. Is there any way to prevent this from happening? Perhaps, somehow to lower the cursor speed, or force an arrow press to register once per press?

EDIT (SOLVED):

The issue wasn't caused by a hardware failure. Seemingly, the cause of the fault had to do with how MirageOS was handling inputs. The solution was to remove all of the batteries to reset the calculator. Since then I've had no issues.

I know somebody who has a TI-84 Plus that has the same problem occasionally. Was it a brand-new calculator or a used one?

It is a used one from online. The calculator came preloaded with various apps, including a text editor called "NoteFlio" wherein the keys work properly. This makes me think that the contacts are probably clean. I'm not sure if dirty contacts would cause this issue anyway.

I was hoping there was a setting that I was unaware of that I could change.

Actually, I just fixed it! Just open up the calculator, clean the contacts and the button membrane for the arrow keys using IPA (rubbing alcohol) and seal the calculator back up. That's all I needed to do and it works just as expected. I'm pretty surprised that this fixed the issue considering that the contacts were visibly very clean. Perhaps a setting was reset when the batteries were out?

There's definitely no such setting. Technically its possible that it had some messy assembly program running on it that was messing with hooks, which would have been removed when you pulled a battery, but I highly doubt this was be the case. The junk in the membrane theory is MUCH more plausible to me, particularly on a TI-83. If that was the issue, I would also expect the issue to be intermittent, which seems to be what you were experiencing.
Happy to hear that all is well with your calculator!

... Yeah, the issue just came back after running a game in MirageOS. I don't think there was any issue with the contacts or the membrane after all. The problem is either some strange intermittent fault, or that game isn't cleaning up after itself properly.

I made a program once that could definitely cause this. Is there a SPEEDKEY program or something? Is it a Batlib program? If so, it might have a key hook that interferes with the OS so that BASIC programs are more responsive. If the hook wasn't reset or disabled, then it would continue to interfere after the program finished.

An app like Noteflio, on the other hand, probably bypasses the OS' key delay in lieu of it's own.

So, if it wasn't some problem with the keys themselves then it does sense if it is a program that could be interfering. Perhaps there could be a bit of assembly code running in a program. If that were the case, then resetting the RAM should definitely fix it. A good process of trial and error and eventually you should figure out.