Sorry for necroposting on my first forum post but I have the exact same issue at the moment. I power PIR sensors from the same 3.3V switching regulator that powers an esp12 module. I took off the anti-inversion diode and the linear regulator, added a 470uF and 100nF capacitor on the sensor supply input. This has been done to two sensors, one is working flawlessly the other one has a false trigger once every half an hour.
Adding HF and LF bypass capacitors with some improvement told me that was a supply instability issue but it's not solving the problem completely. My suspect is that the polarity inversion diode that I took off had a role in the play improving the supply voltage stability.....I'll try to put back the diode and I'll let you know.