Sometimes these taildragger models are designed with a ground attitude that is too high for their own good. If you combine that with a pilot that likes to land REALLy slow you get a situation where the plane is landing at a post stall ( or very high) angle of attack. After the model touches down, it instantaneoulsly transitions to horizontal translation (the ground forces it to) and the ground attitude becomes the new angle of attack which is now a very high but pre-stall angle of attack, and the wing's lift now is higher than before touch down! The model takes off again, goes into stall, touches down, takes off, etc., etc.