'Input' attribute lost in transformation to box or pushbutton

What causes this issue?

The input/output field which you tried to convert into a pushbutton has
the attribute 'input field'. Only 'output field' and 'exclusively
output field' are permissible.

System Response

The system has removed the 'input field' attribute.
It will also, if necessary, have removed other attributes which only
apply to input fields, such as 'required entry' or 'no template'.

Error message extract from SAP system. Copyright SAP SE.