This was all anecdotal from my side and just a couple of friends experience so am not trying to pick on Bosch in particular, but the point is more to do with if an e-bike from one of the large manufacturers does stop working out of warranty it can be a very expensive repair bill and one that the bike owner isn't often able to do themselves due to lack of parts etc. These companies imho have you over a barrel to some degree. The beauty of the converted bike is that not only is the initial cost a lot less, repair costs are also small in comparison and most can be done by the bike owner at home with simple tools ,you don't need to send it back to the manufacturers at cost and inconvenience of not having a bike in the meantime.
I have had no issues with the Toseven mid drive torque sensor motors and it sounds like the Tongsheng is also pretty reliable. I know someone who has had an issue with a Bafang mid drive cadence motor but in my little world I know more people who have had issues with Bosch. Make of that what you will
One of the otehr problems with Bosch is the way the bits talk to each other
If one of the components sees another one is not there then it can disable that missing on - or something
then only an authorised dealer with the correct software can then re-authorise it
a while ago the speed sensor on mine broke
it is only the small things that detects the magnet going past
but when I asked the LBS he said that I could get it online but if I tried to replace it myself - which was clearly easy
then I ran a chance of the whole system failing to work
so it was easier - and no more expensive (ish) if he did it all
in the end he said he got everything ready and unscrewed the old one
then disconnected it and reconnected the new one as quick as he could - and it didn;t realise
but apparently he has seen ones where the same thing causes the whole thing to freeze and the bigger bits are even more sensitive
which does lock you into the dealers - even if it is easy to replace