Increase voltage drop required to saturate PNP BJT to avoid noise
By re-arranging the resistors you can make the PNP much less sensitive to EMI on the switching nodes:







simulate this circuit &ndash; Schematic created using CircuitLab

How does that work?

R2 and R1 are a voltage divider so any disturbance on the wires to the switch is attenuated by R1 and R2 (and optionally C2) making it much "harder" for the EMI to open the PNP transistor.

Optionally you can add C2 to suppress EMI even more if needed.

Do keep R1 and C2 close to the transistor.

What also might help is twisting the wires to the switch: