The quality of Chinese supplied e-wheels is variable - poor quality spokes, thin rim walls and inconsistent wheel building standards can give problems.
These can be minimised by checking a new wheel to see if it has a reasonable level of even tension. Also check on the 'dishing' of the wheel to avoid brake alignment and other problems when the wheel is installed.
Adjustments are fairly easy to carry out and have been effectively covered by D8veh in previous threads.
I can supply custom cut European made DT Swiss and Sapim replacement spokes in 13g and 14g in any quantity. These makes are considered the best available and usually minimise spoke problems if fitted correctly.
If a wheel has had several spokes break or used with a broken spoke, it's possible the spokes will continue to break, even if good quality new spokes are fitted and the tension corrected.
Remember these are bike wheel components, with a powerful motor, rough roads and 'enthusiastic' riding it's possible to destroy any wheel
Alan