In BBH 16.19.3 the rationale for the "missing" dagesh forte is that the second root letter is a guttural. However in the ifs, 3mp and 2mp of the verb nasa' (nun-samekh-ayin), isn't the second root letter the samekh with the first root letter being a nun that has assimilated? If so, then it is unclear why the samekh does not have a dagesh forte