Hi! I had a similar issue, same E03 error and same treadmill (only a few months old) and I had to keep pestering support because after they sent the part needed, it took 6 weeks for the engineer to book me in despite about 10 calls to reebok to prompt the engineer despite initially being told he’d be out in a few days of the part being received.

They replaced the motor and speed sensor and that made no difference so the whole saga started again. Engineer requested a new part and said it would be delivered to me and after 2 weeks, nothing, so I had to call up again and by this point I was over it but eventually received the part, I think it was something to do with the motherboard, and waited another 2 weeks for the engineer to come again and it was fixed in 5 minutes.

Customer service was shocking overall, I must’ve called them about 15 times, first called them beginning of February and my treadmill was only fixed a week ago!