Oh yeah, spokes and hub issues. there are OEMs using IGH hubs that were never designed for the input torque of a mid drive motor. I had one come to me last year with a Sturmey Archer 5 speed fat bike hub that had the sharp edges of the drive pawls worn down to the point they would not stay engaged. When I contacted Sturmey Archer about possible warranty, they said no way as they have never approved any of their hubs for E bikes.
I ended up doing a full overhaul on the hub with a bunch of new parts all at the customer's cost.