On the side is a plastic screw. Unfortunately, neither cross nor slot, but I was able to adjust with some fumbling again so that the machine cut. But that was not so easy. Either the machine was loud again or the movement of the cutting blade was so low that it so not even cut properly.
So really gratifying is not. Mother then had an almost identical hair trimmer (I would almost bet by the same company) and worked to make more than 20 years with no funny business.