Indeed I had the same problem with the rear brake (the most used one in fact). I think that by adjusting the tension of the cable it can be fixed (not done yet actually). But the most annoying thing is that the battery drains immediately when it's 4C outside in dry weather. This left me stranded after 7km of riding, when I could do 20km without any problem. I was able to recharge the battery but the indicator showed 53.4V whereas at the very beginning it showed 54.6V. This morning it was impossible to switch on and charge the battery. The light on the charger never turns red (sign of charging). I have to return it after just three trips... a bit weak and very disappointed.

Hello, indeed, my rear brake also whistles... it seems that it is possible to reduce the noise by adjusting it (https://blog.utagawavtt.com/fr...), but I have not tried yet.

Thank you for your help,
Nicolas

My brakes are whistling too. So if you have an answer from someone who has been able to fix it, please let us know.