I would say you are using a slur rather than a tie, but if replacing the two notes with one dotted note does not solve the problem, then my next step would be to clear MIDI data for that measure.

Is there any chance that another voice/layer/instrument is striking the same note and making it sound as if the note is repeating?

If you send me the file, I’ll have a look. My email is in my signature.

To J Adrian:  hello. I am using the tie tool, not the slur tool. I isolated the track and even when the other instruments are muted, it still plays wrong so I know it's not another instrument. I realized it's playing it wrong in all measures under every instrument with the exception of just a few measures at the beginning. How do I "clear MIDI data" for those measures?

Ok, so I just figured out how to clear the MIDI data: went to Edit, Select All, then Edit, Clear Selected Items, and then checked MIDI and the 3 boxes under it and clicked OK, but unfortunately it's still playing incorrectly.

Is this, by any chance, a tie crossing a barline?

To Mike Rosen: No, like some of them do but the majority of them do not cross the barline. It's weird cause every document up until this point has worked and this is the first one that did not, and I didn't change any settings that should affect it that I can think of besides using the aria player to change instrument voices. Also when I started creating the file, it seamed to be working, but then as I approached finishing it started to act up. I appreciate you offering to take a look at the file, but I'm unfortunately way too anal and don't want anyone hearing it even though it's already copyrited. The MIDI file extracted from this file plays correctly rhythm-wise in Audacity but it unfortunately doesn't have any of the Garritan sounds that Finale does. I submitted a ticket...

Try exporting it as XML, and importing it again. That sometimes helps.

So I tried exporting as XML, but then it's having similar issues plus more issues (dealing with instrument sounds). I'm just going to move on because I realized it's only happening to one instrument in the document and that luckily happens to be the instrument I'm going to mute to sing over for the vocal part. Hopefully it was just a small one-time glitch that doesn't happen again in future documents.