Error with cost of goods module on items with variations

Since recent update I have begun to have an error with variable products and cost of goods module.

While cost of goods module is active I cannot edit variable products.

The product descriptions and product data sections are blanked out, and there is a message in the cost of goods section saying the site has had a critical error.

When I disable the cost of goods module I’m able to edit the product as normal.

Thanks,

Simon