Loose connections.
Loose connections and connectors can kill drivers. It is very important that all connections to steppers are perfect.
An intermittent connection can kill drivers, and not just the Syil ones.
Same channel died twice? Find the cause, or live with it till it dies again.
Once something has run for a month or 2 blame external causes.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.