New interface and variation theme no longer available

We’ve noticed Amazon has recently updated their product interface for editing / adding products.
We’ve come across an issue that we can’t seem to get any help with - wondering if this is an error or if anyone has found a work around?

We mainly sell garden membrane / netting, which comes in various sized rolls. We sell via variation listings.
Since the update we saw a message that states:

The variation theme that you selected previously is no longer available in this category. You can still edit existing variations, but you cannot add a new variation.

Now, from my understanding, we can’t add our product to any other category, as this IS the category for our product. But we’re unable to add a new size to this listing and can’t create a new variation listing as size is not longer a theme option in this category.
Anyone else having this issue, I would think this is like a massive oversight on Amazons behalf.