My version of 135/4 Macro for P67 is the later SMC Pentax type, and does not exhibit this problem. But focus creep or zoom creep is an easy fix, by yourself.
You just need black electrical tape, cut them into trapezoid shape, and stick to the focusing/zoom helicoid. You need to experiment with the length and width of the tape. Sometimes you might need to apply it to both sides. One visual example of Nikkor 75-150/3.5 Series E lens, which suffers from zoom creep, with the tape on.