If you do a cycling workout with a cadence target, the actual cadence target displayed in game may only be half of the actual target.
Example: Your workout has a block that's designed with a cadence target of 84. When you actually reach that workout block, the cadence target shows up with a value of 42.
As we aren't aware of an actual workaround yet, you may want to avoid workouts that include a cadence target. As long as you use a trainer with ERG mode, you can still have power targets while riding at any cadence you want; your trainer will automatically adjust your resistance to meet the power target.