Cannot Save edit of AutoSKU checkbox option

AutoSKU was working normally. After installing a number of add on commerce modules and making changes to Term Reference and entity reference fields on one product type, I can no longer save changes to the AutoSKU enable (or any other AutoSKU setting changes) on any product type, including new text product types with minimal fields.

dblog shows no errors or notices when product type is edited and saved. Returning to edit product type shows that the changes made to the AutoSKU settings were not saved. In effect AutoSKU cannot be used as it cannot be turned "on".