Personalizations using base instead of the customization they're built on

So, it looks like employees are building their personalizations on the correct parent, we use the “OrderEntry_V2.1” customization.

However once they create their personalization, when they open the window (in this case Order Entry), none of the customization loads. None of the fields that were added in that customization or anything, like their personalization is just of the base.

If I delete their personalization and they open the window, the customization loads correctly.
Any ideas?

If the personalization was built before the customization was complete, that may explain the issue.

It was not. We went live this past weekend, and the customization has been in place since then. It was built in our pilot environment a couple months ago and moved to live a few days ago.

People just started building personalizations this morning, there were none beforehand.