I have created a couple of custom post types with meataboxes. All of a sudden some of the meta values are no longer saved. For example, a meta value with the key _cp_url is saved, whilst the key _cp_coulour is not (both are text fields).
It looks like keys that exists in other cpt's meta is saved, biut not new ones.
I don't really get why this is happening. Any idea on where to start?