Common eBike problems and solutions

Hey everyone!

Been lurking for a bit and finally decided to jump in and start a thread. I'm deep into planning my next custom build – thinking a mid-drive hardtail for some off-road adventures, maybe 1000W Bafang. For those of you who've gone the custom route, what are some of the most common issues you've run into with your DIY eBikes, especially after a few hundred miles or on tougher terrain? I'm trying to anticipate potential headaches and figure out the best solutions before they happen. Any war stories or preventative tips would be awesome!