Taking a standard pericope -
Cattāro me, bhikkhave, jhānā. Katame cattāro? Idha, bhikkhave, bhikkhu vivicceva kāmehi vivicca akusalehi dhammehi savitakkaṃ savicāraṃ vivekajaṃ pītisukhaṃ paṭhamaṃ jhānaṃ upasampajja viharati.
You actually need to read the verbal cluster underlined as one. Some call this a "periphrastic" construction, of which Warder has much to say (p.233). To cut a long story short, upasampajja
would be the absolutive/gerund of upasampajjati
(attains/enters), while viharati
(abides/remains) functions as a "mere" auxiliary verb.
As to how an absolutive/gerund can be interpreted, check out Dymtro's lovely post here - viewtopic.php?f=23&t=16316#p232556
. There was a further discussion of another important absolutive vineyya
here - viewtopic.php?f=23&t=15707#p225276
Both translations are permissible. Bhante Anandajoti opted to translated the absolutive as a past action completed before the auxiliary verb. Ven T translates the absolutive as a gerund, ie contemporaneous with the auxiliary verb.
I don't see (at least not yet) any doctrinal dispute simmering beneath either translation.