Regarding UART function of this type of controller.
I've noticed that processing time of incoming stop bit (from communication partner) deviates within 500us range.
Moreover, I would not say that it processes some sequent/parallel tasks at the moment. It's at idle state.
In other words, the controller responds always at different time, thus causes issues in the bus.
-How do I treat this misbehaving?
Perhaps someone faced with something similar. Different controller or so.