Definitely, the main source of the problem is beveler. Having become interested in working with leather 2.5 years ago, I bought such a Chinese set of stamps “one and a half ten for 10 dollars”. This Z-B197 of terrible look was definitely in it. My disappointment knew no bounds - I could not get even a miserable semblance of result. It is good that this first disappointment did not put an end to attempts. How happy I was when I bought a few inexpensive (3-5 dollars apiece), but normal stamps, I managed to get a normal bevel. Do not let disappointment from bad tools, which in principle can not fulfill their function, stop you.
Good luck!