The page doesn't receive an object. Perhaps because of access rights or because there is no object passed to the page. Check the access rights for the user, and try to open the page from a microflow and see if there is an object passed to the page?
Could it be that you are somewhere using the system member Owner somewhere in your model? And could it be that you set this member on a later stage and thus have records where the owner is not set and records where the owner is set?
I assume it came from one of the record’s calculated fields that included calls to Java’s GetGUID and GetApplicationURL. Changing it to stored with the appropriate event handler (figuring out the right combination of after/before commit and steps’ commit value was tricky though) seems to have solved it.
It seemed to have come from a QR code widget in responsive mode. Removing the responsive option and placing it into a container made the error disappear.
Revisited this old widget I created 4 years ago as there as a Support ticket regarding this widget. Although Community Support, I took a look at the issue and Patrick seems right, it was in the responsive mode. I fixed the issue in version 1.1.0