BMW K100 – engine dies off

Wishing for a nice evening Last year there was a problem. With stronger braking the engine dies off regularly. I simply find no connection here. Looks as if this only fits in the speed range 1500 -2500. On the advice of my mechanic of the familiar I cleaned contacts on a (control?) device. After that the push-off function worked much better. Motor still dies off. Do you have an idea? lg