Signed forms are losing the signature, even when the field is Disabled.

It shows disabled but does not show the signature

The signature can only be seen on the step where it was signed. In the past as long as this field was disabled/read-only it would not lose the signature, allowing users to append sections of new data to the already signed form.

Appending sections of new data to a previously signed form is very common, think of the I-9.