I own 3 electric bikes and no issues, one is Bosch, the other is Mahle/Specailized Mid Drive and the final is Brose/Specialized. In terms of motor replacements having done warranty going on 10 years now I have replaced very few motors in quality bikes. Probably of the bikes my previous shop has sold we have replaced maybe 2-5% of the motors in them and that is being generous and that is talking about 7 years of big sales.

I know some of the early Fazua stuff wasn't all that exceptional for some people but I have yet to really put any time on one and we never had anyone that sold them in our vendor list that we would have stocked so I cannot speak to that stuff. Mahle at least with their Mid-drives they do with Specialized are excellent but hub drives are known for more issues generally but not always motor quality more broken spokes and stuff like that at least on the higher quality stuff.

I do know that getting a bike with good support is handy. Bosch is the absolute best out there hands down. However Shimano, Brose, Specialized...all have excellent support and are easy to deal with and I can still get parts for some older bikes.