I have just experienced the same thing. and posted about it in forum and linked to this post as being similar. not causing me any real issues but I thought it might be useful to know that had same thing happen. I have been using Illustrator for 20+ years never noticed before.

I was just was creating artboards for project and I noticed the numbering system has replaced 7 with an 8.

I added a couple of extra layers and seems to add them fine with numbering. not urgent. Just highlighting it as seems another user has also had similar issue. https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs/suggestions/39220252-artboards-with-the-same-number

Artboard number sequencing is not correct post 33, Artboard 34 is missing

The software starts skipping random numbers when there are more than 20 art boards. It feels like ai can't count??!!!??

@Amber, sadly, these steps do nothing for me, and their variations too. No skips, no duplicates... You are lucky to be able to keep Ai live for 5 days, without a crash :) But yes, I confirm that it never happens if it was launched recently, and always happens in the heat of an action, with Ai being launched for a while, with a lot of tabs.

Why it often happens at the eights artboard though...
Thanks for the comment, the searches continue.

I have the steps to get this to show up on my computer(Mac). I notice with a different file and was able to get it to happen again with fresh file. My issue was artboard number 8 would be skipped and number 9 would be duplicated.

Starting with a fresh file with three artboards.

-Go into artboard tool
-Delete two of the artboards
-Duplicate the remaining artboard over the the right holding shift and option
-Do this step with the second artboard
-Select the three artboards and duplicate them down holding shift and option
-Repeat the last step and find that what should be artboard 8 is now artboard 9 twice

Something I noticed that if I restarted ai(quit the application) the bug would disappear. I couldn't recreate it then and the file I was working in was fixed. My thought is it might be a combination with having multiple tabs open and have your application open for days on end. When I found this bug I had five tabs open and with two of them needing to be saved(having an * by the file name). I believe ai was opened five days prior without being closed out. I am not a coder so I don't know if this has anything to do with it but this was my experience.

I just got this message from Illustrator when trying to export one specific artboard. I have never seen this message before. The artboard it self is numbered 79, but should be nr 78. I looked at the artboard menu and the info on the artboard and there it is number 78! So it worked for me to export nr 78 but this is a very strange error. Why is this happening?

Created a new document and it still is skipping one number (56) and duplicating one (59)! Is there no bug fix for this 2.5 years later??? If I do the option Lisa mentions, it does export ok but the file itself is still incorrect.

When this happens to me (happens randomly) it is always after I save the original file. A workaround is to export before saving. Another workaround I have found is to 1. select artboard tool 2. select ALL artboards (hold down shift and click each one) 3. click on Artboard Options 4. under the name option, type Artboard 1. This should reset the names of the artboards. 5. Export. Do not save the file first or it reverts back to the incorrect artboard numbers. Hope this helps someone.

Having the same issue. My file will allow me to create new art boards, and or drag a new art board. BUT it will always duplicate number 10 ( skipping over 9 ), duplicate number 12 ( skipping over 11 ), duplicate number 15 (skipping over 14). Does not seem to be related to the content in the file, I can lock the layers and the issue still occurs. Manually re-ordering or editing the names does not solve the issue. Deleting and recreating the art boards does not solve the issue. Saving as and creating a new file does not solve the issue. Staring over with a completely new file does not solve the issue.

Artboards and paste in place are a nightmare.

https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs/suggestions/36451072-paste-in-place-does-not-work-properly

Stefania, a cool observation! Definitely a bug... I just think it night be a different bug. I suppose it should be reported separately. Can you do that, please?

OK, I just posted a comment and I noticed something odd in the video, so now I think I have found what action triggers this bug. Please watch (and wait for it): https://www.screencast.com/t/Xxugi3ai8LAQ

The issue I'm facing might be connected with this one. When I have multiple artboards and I start to rename them, sometimes, completely randomly, renaming one artboard, automatically renames the one above it ending up in two artboards with the same name. Look what happens here: https://www.screencast.com/t/ywyCAyfhEOH

There are two '26' artboard.
I can't find '25' artboard.

Quando temos muitas pranchetas, as vezes chega num limite em que alguns números se duplicam e não consigo exportar as pranchetas duplicadas

アートボードナンバー　96がなくて、97が重複
アートボードナンバー　113がなくて、114が重複しています。

Reset illustrator preferences can help!
Illustrator > Preferences > General > Reset Preferences > Restart
My Artboard numberings got fixed!! But adobe still gotta fix this issue asap

複数のアートボードをつくって作業していた
↓
保存してai閉じる
↓
ai開く
↓
アートボードが1つだけになっていて　「アートボード１」ではなくて「アートボード９」のみある状態。
↓
直前まではアートボード４までしか使っていなかった。９はどこから？なんで？

XY軸もずれて仕事に影響　困る。

これに限らず複数回起こっているバグ。
なおしてください

Document has 42 artboards in total and there are two sets with duplicate numbers I can't change. Very frustrating to see how long people have been flagging this for with no fix. It has messed up my exporting of logo files and meant I almost sent the wrong ones to a client!