Disadvantages
Unlike many other drive mechanisms the cycloidal drive is not backdrivable, the input and output shafts of the cycloidal drive can not be reversed. This is because rotating the output pins will not rotate the cycloidal disc in the correct way.
Also, the eccentrically mounted cycloidal disk will cause vibration in the drive which will propagate through the drive/driven shafts. This will also cause increased wear on the exterior teeth of the cycloidal disk, as well as the interface with the output roller pins due to small relative motion caused by the vibrations. A second cycloidal disc installed a half-rotation relative to the first will balance the input shaft and reduce vibration.
Read more about this topic: Cycloidal Drive