The accounts that name a place do not name the same one, they are all late, northern and secondary, and no site has ever been identified on the ground. Nobody defends a location, so this is a gap in the record rather than an argument between camps.
What would resolve this An inscription naming the assembly, or the excavation of a monastic complex in Kashmir or the north-west of the subcontinent large enough to house it and carrying Sarvastivada Abhidharma material of the right date.
OpenSouth Asian archaeology and epigraphy, working with Buddhist studiesEtienne Lamotte, translated by Sara Webb-Boin, History of Indian Buddhism: From the Origins to the Saka Era