Six Flags Discovery Kingdom (SFDK) Discussion Thread in Theme Parks, Roller Coasters, & Donkeys! Posted June 11, 2016 Damn, its really surprising to hear The Joker is having trouble. Other than LR (which was because of the launch), I don't remember hearing other RMC coasters having trouble. Of course it is not impossible, just surprising. Wicked Cyclone had the same problem for the first 2 or 3 months. It's likely a SF PLC thing.