The immersing rope tends to slip in the integrated cam-cleat and to let go the hydrogenerator. Two reasons are possible, there’s too much strength in the rope, the rope material is too slippery.
Attach the immersing line to the bracket instead of the leg. Use a block or a low-friction ring attached to the leg in order to divide by 2 the effort in the rope. See drawing below. Use a less slippery line (pre-stretched polyester). Enhance the cam-cleat spring power. Harken proposes optional springs (ref Harken MS-006). Depending the model of your hydro, the hole drilled is too far forward : you can drill a new hole 15-20 mm backward to have a more efficient multiplication of the strength.