When you use custom mockups as the default view and load the product screen, usually the custom mockup is shown by default on the product page. When you click on Personalize and open the template form, the view switches automatically to the first real-time preview, usually the front view.
On the new foil cards - flat holiday variant (didn’t test on invitations + postcards) - this behavior is broken. Please see the screenshots for details. Happens on desktop, Win 10, Chrome + Edge, logged in and out. All other products with custom mockups I’ve checked work correctly. P.S. the mockups are pretty fresh but this never was an issue.
Here is the related product: https://www.zazzle.com/sable_collie_angel_pet_loss_sympathy_foil_card-256214375780626556
I made two more cards, same problem.
P.S. there is also a strange behavior when adding custom mockups on these cards, which does not happen on other products I tested: Adding the mockup works fine but apparently, it is not automatically set as default - I had to set it manually (edit details). Plus the small view in the product listing looks strange the first time you set it - some sort of a pattern of the video. The problem is solved after you add the custom mockup again.
I hope, I described it clearly. If you need further info, just ask.