1 and 4 then 2 and 3 should spark alternately , I would say you might have a faulty coil , the half that does cyls 2 and 3 , it is breaking down and can only muster 33% of the HT required , as the coil has 1 feed and 2 switched earths , 1 for cyls 1and 4 the other for 2 and 3 , it is sparking at some point so would kinda rule out wiring to some extent ( not completely though )

Try a known good coil first then check wiring continuity back to edis module , then try the edis module itself isthe route i would take .