Keystep sends MIDI CC messages as sequencer transport control messages, which helps nobody but particular DAW users. These really mess with Waldorf synth users especially, as the CC's send are also the same used by Waldorf for various filter parameters.
The way to fix this is to use MIDI Control Centre turn off the messages or to change them to a CC number that isn't used by the synth, which with Waldorf synths is not many. I use CC124, which is Omni Mode Off on every MIDI synth ever. Omni Mode sets the synth to respond to ever MIDI channel it receives and is usually only used for testing stuff, so really shouldn't interfere as much as sending a CC50=127 message everytime you hit play.