How long have you owned it, did it ever work correctly, do you have a manual for the bike, and explain every detail you can think of, take your time, on exactly HOW it APPEARS to be in mode 3?
Carefully check that Modes 1, 2, and Walk, might just be doing Very, Very little and not quite Nothing.
Also, you have an ebike made by Manufacturer Ecotric, with a model name of Dolphin. Not the other way around.
With the limited information available, it Could be the controller, it Could be something else.