I assembled the pump again because three engineers at different workshops do not see a problem with the gears. I've verified that by calculating the numbers and estimated a radial meshing shift between pump and crank gears of the order of the manufacturing tolerances for gears. Therefore a slight gear wobbling can be tolerated.

The shaft of my oil pump is not really straight with 0.15 mm offset at the taper fit. This in turn contributes to the axial up and down gear wobbling of about 0.5mm. I now wonder if the small pump gear is shrinked onto the axle and if I can detach it so that a new axle can be manufactured. I know, this is a pretty wild question but perhaps some colleagues do have an idea or even a spare.