Having this same issue, but mine seems to happen more on higher number of artboards, usually 80+, but sometimes it happens at the lower numbers as well.

PLEASE HELP!!!

The numbering of artboards is consistently wrong in the newest version of CC 2108

When creating artboards, artboard no. 10 is skipped and two artboard no. 11 are made.

I have a similar error. Page 6 appears to be inaccurate. I have 7 twice.

1 Artboard 1
2 Artboard 2
3 Artboard 3
4 Artboard 4
5 Artboard 1
7 Artboard 7
7 Artboard 7
8 Artboard 8

Since Ashutosh had closed comments to same report (https://illustrator.uservoice.com/forums/601447-illustrator-bugs/suggestions/32026201-artboard-numbering-error), without getting it fixed, I will AGAIN add comment here.

This bug makes me loose money.
I've sent you an email through 'other support channels'.

This is more than just art board 7, it also happens at 21, 23, 27, 31, 37, 42....

Latest version of cc 2018 has a glitch when creating multiple artboards it skips 6 and labels two boards as 7 before continuing on. This makes it skip the 6th board when exporting due to the fact both are named 7.

All new documents but thanks - clearing preferences resolve it :)

when open more then 9 artboards, illustrator make the same page number for some of the artbords (look at the video attached).
it open 1-9 artboads normally the next artboard is no 10 but 11 and also the one after it also 11 then until 14 it's also OK but then no 15 artboard but 2 16!
it make very hard to export the artboard that have the same page number
and generally really confusing

When I drag to copy an artboard it creates a new artboard. So when i try to export that new artboard it shows error and says it doesn't exist.

It also happens the new artboard to have number that already exists.

I am running into the same problem and I it doesn't work to export artboards that get stuck within the numbering glitch.

Same Problem here.

It was caused specifically when duplicating having more than one artboards selected using alt+drag with the artboard tool. When tried to export, it just exported the first one, ignoring the second.
As well, restarting the Illustrator fixed it.

Upon restarting Illustrator, file was fine.

I too am having this problem. But duplicating dartboards 15, 19, 28 and 32 out of 32 artboards. When exporting, only saves the second duplicate. Deleting duplicated artboards does not help.

https://adobe.ly/2FieEfr

I have this error too

I'm having a similar issue, I have two 15's and only one exports..

When I make extra artboards, sometimes the numbering doesn't work and it gives problems with exporting files.

See the file I included

1 Artboard 1
3 Artboard 3
3 Artboard 3
4 Artboard 4

Also there is no 18...18 is 19.....

Artboard 15 had been named 16 for quite sometime now, hadn't had a problem much except if you export 15 and 16 at the same time it would override "15" because it is 16

I created a new document and made up empty artboards and it still had the bug but restarting the application seemed to reset and it works now.