EX4 works with 500Gb disk, but not 4 or 6Tb

I inherited an Ex4 with 4x4Tb drives in working condition. Did a factory reset. After finishing, EX4 booted but showed 4 red LEDs with “Drive failed in bay 1, 2, 3, and 4” error. I removed the 4 disks and checked on my windows 10 machine: all 4 are good. I formatted, …, removed partition, etc, etc, but nothing worked. EX4 always shows same error. Inserted a 500Gb disk and that one works in all 4 bays! => Bought 4 new WD 6Tb NASware 3.0 drives. They give me the same error. Upgraded to newest firmware, but that didn’t help either. All larger drives make a ticking noise while booting.

=> Any idea what’s causing this error?

Problem solved! A faulty power-adapter didn’t provide enough juice to spin larger hard drives. I swapped the old one out for one with higher specs (coming from another external WD harddrive) et voila, everything’s working now.