Let me make myself clear with an example.
I was developing an HTML web resource and I was changing the value of a field only shown on the footer. In order to be able to change the value of that field I had to place it on the form as well and hide it. This means that I set, from the form designer, the following properties:
- Visible by default = false
- Field is read-only = true
So what you should do is: Hide the field on the form but don't set the field to be read-only as shown below.
If it is a bug or it is normal, I don't know. If someone knows the reason of this behavior please let me know.