A semi-free rotating crankshaft actuator (80) for an oral healthcare appliance comprises a chamber (82), a spring loadable plunger (85), and a crank mechanism (88). The crank mechanism (88) comprises at least a drive pin (90) rotatably driven about a drive axis (96), and a crank shaft (94) semi-freely rotatable about the drive axis, wherein the crank shaft (94) couples to the spring loadable plunger (85) and is partially driven about the drive axis (96) via (i) the drive pin (90) in a first operational mode, (ii) the spring loadable plunger (85) in a second operational mode, and (iii) the drive pin (90) in a third operational mode that comprises at least completing an incomplete actuation of the plunger (84) from an undesired end position to the desired end position in response to the crank shaft (94) pushing the plunger (84) from the undesired end position to the desired end position.