Early in my career I had one of my worst memories flying, was doing a post maintenance test on a Robinson R22 Mariner (fixed floats) The task was to carry out an autorotation at Vy (53kts) at minimum weight. This procedure is to ensure the pitch links are correctly adjusted so the MR-rpm don't drop too much in a engine-out scenario with all the mess that bring along!! I remember setting up for the auto, lowering the collective full down and rolling off the throttle, splitting the needles.. The RRPM started to drop instantly, the horn sounded and the RPM continued to drop past the value on my papers, so I started to recover by rolling on the throttle full open and helping the engine by flaring, although relatively high at that time, the focus was to get the RPM recovered. I managed to do so, but only a few feet over the runway.
Due to the floats, the Mariner has quite a different feel in auto as the floats makes a lot of drag and apparently therefore the pitch-links need to be adjusted from a standard model. This was rigged as a standard by a mistake. I had a very convincing chat with the company's director of maintenance, and he assured me that the mechanics would correct the rigging and I should go try again!
Understandably, I wasn't all too happy about that though.