I had the same steps on my 2017 RRS about 2 years ago they did this and I did the following and the problem never happened again.

1) Give them a full clean with a pressure washer to make sure no mud etc
2) Switch them off in the settings menu for the side steps
3) Go for a drive (min 15 mins)
4) Switch off and lock car and grab a coffee so systems go to sleep (10 mins I think?)
5) Start car and switch steps back on
6) When you next stop give the moving parts a good spray with silicone spray (not WD40)