Oracle Forms - display item - database item property changed to no

I have a very annoying problem.

I have several hundreds of oracle forms in my production environment, that are working correctly, but suddenly some users tells me that some values in a specific form are no longer been saved to the database.

When I reopen that form I see that the property of one or more display fields are changed from database item = yes to database item = no.

So the fields is no longer saved, but I am 100% certain that I did not change that property.

I think it happens when I open the form, add something to that form, build, compile and save that form.