You should check the clutch drum of your Mantis tiller.
In order to do that, you have to disengage your engine from the transmission.
a) Under the engine, you should remove 4 of the 10 screws to get to the clutch drum:
b) Once the flange in hand, you should check that the black cover does not exceed of 5 mm the lip of the mounting flange:
c) If it does exceed 5 mm, you should lightly tap on it with a mallet to put it back in place:
