Plugin not working after upgrade

We recently upgraded to WP 4.6 and WooCommerce 2.6.4. Since then we have the following issues with variable products only:

1) The fields where you type in custom availability messages do not retain and display a message that is typed in after updating the product page.
2) The “Save changes” button below variation detail fields does not save a newly typed message, and in fact deletes any existing custom message so that the default message displays on the page. After clicking “Save changes”, the variations fields collapse, and when the variation that was modified with the custom message is expanded, the field is empty.
3) Typing in the custom message and using the “Update” button in the upper right to save the page does modify the message, but after the page is refreshed the fields are displayed as blank. The database does retain the saved info – it’s just not displayed.
4) Since all of these fields display as blank on all variable products, if we leave those fields alone and save the page using “Update”, it saves BLANK for those fields to the database and reverts them all to the default message.

Thank you for your assistance.