Hi @iliasweb, @haydin81 and @adriangrzybek . I ran into the same problem, but I was able to solve it and thought I would share in case anybody else has the same troubles and happens to find this thread via google as I did.
I don’t know why the problem appears, but it seems that for some strange reason, when you have more than one product in your cart with custom fields, it tries to evaluate all required fields for the other product(s) as well, no matter if they have the field or not.
So while I could not get rid of this error itself, I tried to “outsmart” it; I thought that if the algorithm somehow checks for a required field in a product which does not have it, maybe it will also check the requirement parameters, too, and that did the trick for me: I simply changed all fields requirements from “Always yes” to “Only if visible”. Which, for visible fields, is effectively the exact same functionality; but now, the plugin checks that those custom fields are not present (and therefore visible) in other products, and doesn’t see them as required anymore.
I hope this helps. It’s a strange workaround for an annoying and potentially plugin-breaking error, but it worked perfectly for me.
