Good afternoon -
Strange case here and I can't seem to find any background after an afternoon of Google/forum searching.

I have a file that is recreated annually with tabs created for each month's work. The 2018 file had no issues, but, the 2019 file is causing issues.

When, say, the March tab is clicked on, the previous/February tab opens, and so on. To open the latest tab, you must click to the right, beyond the "new tab" plus sign.

This file was submitted to us by a client (as was the 2018 file), so, other than it being a .xslx file, we don't have much else to go on as to how the file was created. One would think it was just a "Save As" from the 2018 file, but, as previously mentioned, that file was fine.

Has anyone seen this before, or, have any idea what the issue could be... and any possible fix? As the information month to month varies, and there are several people accessing this file monthly, if one isn't aware of this issue or just isn't paying attention, there is a pretty high risk of invalid information being pulled in. So any help would be greatly appreciated.

If more information is needed, please let me know, and I'll gladly supply what I can.

Thanks,
Katy