it's a known AC problem with Fanatec Rev Lights. even with FanaLEDS it is hit and miss. i ended up using this software, and had no issues after whatsoever and has tons of options! http://www.eksimracing.com/
Also If you dont like some of the way the display/leds reacts, hit up the advance options and play around a bit. SliMax can do OH Soooo much compared to Fanaleds.