Minor issue with Mulit-Variant and Notify Me button

[sixdeuces]

I have successfully set up a product using the new Multi-Variants from v3.0.6. Some of the variants are out of stock, others are in stock. Config is set to display "Notify Me" when out of stock.

When viewing in the front end, the product is loaded with Cart button as normal.  (The default variant is in-stock.) When I select an out-of-stock variant it changes to Notify button as it should, but when returning to any in-stock variant, the Cart button never returns.

VM3.0.6
J3.3.6

[Milbo]

Thank you.