Something that's relatively well known but worth repeating again and again...
Aluminum forks do not mix well with hub motors, especially the more powerful ones. I hope someone can weigh in with more detailed explanation but I have heard this warning repeated several times and heard of a few instances where forks have broken. I've heard of one person whose fork broke while riding and he broke his collar bone.
I installed an front wheel E-BikeKit on my Electra Townie to replace the old Wilderness Energy kit ... it's a fantastic kit, BTW. The kit comes with a torque arm which I dutifully installed. I went to check the install and that was going to require pulling the motor/wheel and discovered that the dropout on the fork had broken. (picture below)
I was sure I'd checked that this bicycle had steel forks. But --well-- they weren't. One way to check is to read the side of the fork, and maybe the manufacturer would have written "Aluminum" on the side of the fork. In this case the manufacturer had written "Aluminum" on the fork, so obviously I missed something in basic reading comprehension. The other way to check is - does a magnet stick to the metal. If it's steel the magnet sticks, if it's aluminum the magnet won't stick.
Fortunately this did not break while riding the bike. Thank you universe for ensuring it did not break while riding.