Thanks for helping out.
I have two CPTs: “Webshops” and “Acties”(promotions in Dutch).
Besides that I have WooCommerce installed which created the CPTs “Products”, “Variations”, “Coupons” and “Orders”.
I registered “Webshops” as a CPT-onomiy and attached it to “Acties” and “Products”.
I don’t have any CPT-onomies that used to be regular taxonomies.
Because the problem only applies to the “Products” CPT, I figured that unlinking “Webshops” should at least make it work again, but it doesn’t.
