>Also, do you know if this affects all XS based objects or just SAPUI5 ones?
I believe it only effects static web content - not xsjs or xsodata.
>They are applied to production via delivery units if that makes a difference.
I don't believe that applying via delivery unit would make any difference. The content would still stop working. During delivery unit import, changed objects would be activated and then this activated_at date would change and trigger the problem.