It's back to presciptive and discriptive grammar.
I have heard
deber de sentences where it clearly meant "should" rather than strong "have to", and I never paid attention to it until these posts. It makes sense to me that
deber without the
de is much more imperative.
Just read these two examples, and you will pick up the fine difference in meaning.
Debo ir al médico. (I have a lump on the side of my neck
)
Debo de ir al médico (It's been a year)
Thanks to the person who asked the question, and thanks to all who responded.