Plugin thinks Additional Products are Coupon Codes

We’re using a plugin called TM Global Options which allows us to easily let users select our products in various colours. If I set up the discount as “Buy 5, get 5% Off” and I add 5 of the same product to the cart, it will apply the discount as it should.

If I then add 2 of the same product (in a different colour) to the cart. it will remove all discounts. But if I uncheck the “Remove any bulk discounts if a coupon code is applied” box, it all works as expected.

I’m not sure why it believed that the additional products are coupon codes.

Please advise.

Thanks

https://www.ads-software.com/plugins/woocommerce-bulk-discount/