Just FYI, but without SW support it is illegal (SW Piracy) for you (or anyone in same situation) to download any new EX SW than what ever version came with your switch originally, unless you purchase Junos @ list price of $10K per SW release. So for you to even try to use 15.1 is actualy illegal, with SW maintenance contract of new SW purchase.
Yes EX products have [free] Limited Lifetime HW Warrenty coverage, but SW coverage is NOT Free.
FYI