Forms and select fields

Hi. I have this problem: in a reactive form if I change the value of a select field -1- (in edit mode), the validation of the form don t work (that mean the save button -2- is always disabled). This situation happen also when I try to insert a new form if the select field is the last field of the form (in the picture if -2- was in place of the url image field).

see this 20 sec of Utube video.

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Add Course Title Input invalid Input valid ... Input invalid Input valid ... Save Cancel

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