Issue with Availability notice on variable produtcs

Hello.
This is a nice plugin. Thank you.

I have an issue though with the Availability notice on variable products.
Let’s say you sell a pair of shoes and size 40 is in stock and size 41 is not so you set it as a pre-order. Selecting size 41 on the frond-end shows the Availability message as expected. The problems is that when you switch to size 40, which is not set as a preorder, the Availability message stays on the screen instead of going away.

Is there a way to fix this?

Thank you again,
Vassos