Nope, it is the known old bug. First, try to update your Ai, it is more stable in recent version (for this case I mean). Second, as a cure method, try to close-reopen Ai, it usually helps me.
And there are major reports about this, please vote all you related can find:
https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs/filters/new?query=artboards%20number

Could be my older system I suppose

Artboard #3 has been consistently showing as with a 4 by it. Is this just a glitch on my system?

Hi there, I am facing the same issue. I have a file consisting of 64 artboards...but it duplicateds certain artbords and others dissapears. for example

"35, 36, 38, 38, 40, 40, 40.."

when i try to delete a "duplicate " artboard it just moves the double numbers up. This means, that when exporting, it pics up the two 38's as one, so only exports 1 image"

and i have no clue how to fix this....

In version 24.3 there is an issue with duplicate artboard numbers when creating a copy of an existing artboard (ie: it will skip from 3 to 5, and repeat 5 twice) and on export will only export one of the duplicate artboards. So, I had a file with 8 artboards, but two of the numbers were being doubled when I created them as copies so it only exported 6 of the 8. I wasn't able to find a work-around to export these duplicated artboards so I ended up downgrading to V 24.2.3 and it fixed the issue.

Artboard 113 gets skipped and is labeled as another 114

Yes, I'm having the same issue. Here is my file. please email me back.

I am currently having this problem

SOLUTION: Save your work and restart the app. It will fix the bug.

I am having the same issue. Artboards won't export as they have the same #.

I am having the same issue as well. :(

Artboard Number 5 gets skipped, and 2 dartboard 6.

Same error

Same, artboard numbers are 1 2 4 5 5 7 7 8 10 10 and after 10 the numbering returns to normal. Creating a new file doesn't help, same issue occurs.

Just noticed that Illustrator CC artboard serial number 52 is replaced with 53. It's confused me to do some amendments on 53, instead I did on 52. Adobe, please correct it.

Illustrator has a bug in artboards. When I create the 18th artboard, the program jumps and creates an artboard with the number 19. And when I create the 19th artboard the program displays two 19 artboards.

When creating artboards, doesn't matter if they are within a new file or existing, Illustrator skips 3, has two 5s, skips 7, has two 8s. Still happens when deleting/adding in the same file, or creating a new file.

same issue! Artboards 29 29 and 31 31.

While this issue is fixable through restarting a clearing preferences, it caused a great deal of trouble for me and is really frustrating. I had boards 9 and 12 duplicating, even when creating a new layout from scratch. When trying to export screens for a presentation it deleted (or overwrote, no way to tell) the duplicates, leaving with a project missing two slides. Very glitchy, very bad.

Hello, im currently having this exact same issue, it happens frequently, im a mac user. How did you solve it?