Nothing, I tried again to create the bundle from scratch, but still same result.
I got also an error while I was creating the bundle, like if the website crashed (something like 'ooops... that's infortunate, not your fault' (sorry, I didn't noted down. Then refreshing the page it went back but was trying to add by itself an asset (the last one Spooky Background) that I didn't want to add.
In the end I managed to add all the required asset with proper discount and still get the same error while publishing.
This is the history of my attempt:
1)
construct.net/en/game-assets/seller-account/my-bundles/8-bit-pixel-art-game-41
My first attempt originally created before the change with unlimted license, I re-added the assets after the changing.
I renamed adding "_OLD" in the title and then proceeded to create 2)
2)
construct.net/en/game-assets/seller-account/my-bundles/8-bit-pixel-art-game-46
This is the one that I recreated before posting the bug and gave me the issue. It's the same you have tried to edit.
Just a few minutes ago I added "_OLD 2" to the title after reading your post and seeing that the result was still the same. Then I have created 3)
3)
construct.net/en/game-assets/seller-account/my-bundles/8-bit-pixel-art-game-49
Once again, I have created everything from scratch, but got the same error.