you said buzz, not hum
it is possible one of the cartridge wires is loose and causing a buzz, usually it will change if you touch the bottom of the cartridge with your finger.
If so, remove, tighten, reconnect, or put new wires.
The ends may be different sizes
"Ortofon SH-4 headshell and Ortofon cartridges’ terminal PINs diameter is 1.2 mm, while Ortofon headshells’ PINs diameter is normally only 1.0 mm."
Sometimes insulation wears off a tonearm wire within a tonearm, or where a wire exits a tube and is subject to movement. If can happen inside a tonearm, nothing but a re-wire will solve it.
Also, some tonearms, a 5th wire is the ground for the tonearm, sometimes something happens. That’s why DIN connections are 5 pins. You can make a separate loose test wire out of any wire and attach one end to the ground on the preamp/amp and then touch various places on the tonearm and hear if the noise stops.
I once took a cover off, and found that the inside connection of the ground connector was not good, I loosened, scraped away some paint, tightened and soldered, noise gone.