8.15.15 - update all out of date themes issue

Hi I used the update all the themes button in sandbox with no problem. The styles stay pretty much the same. But I see a lot of different changes when I did the upgrade in other sandboxes.

We do use our own custom theme. It’s the same themes in all environments. I don’t understand why updating the theme button would work differently in different sandboxes. Can you please advise?

Jin~

Are all of the sandboxes on the same version 8.15.15? 

Thanks!
Karen

Yes. 3 Sandboxes are all on the same version and same theme. 2 of them have the UI impact. 1 which was upgraded earliest one month ago  is fine.