Check Box in Cart form not working

[p.barg]

Hello,
I'm trying to set up a shopper field of type checkbox that is shown in the cart form.
The checkbox is shown correctly where it should be, but no matter if the visitor checks that box or not it is always shown as unchecked in the backend.
If the checkbox is displayed in the account maintenance, it shows correctly whether it was checked or not.

Any explanation?

Petra

Joomla! 3.8.8, VM 3.2.14

[GJC Web Design]

is it  inside the cart form?

[p.barg]

It's right above the customer notices area