Periodic Intruder Alert from one PIR

[RobGG]

We went on holidays for an extended period.  The system was armed.  Three days after arming a PIR gave an Intruder Alert at 03:53 (time from log), the System rang me. I disarmed system. I checked a separate eufy camera - no intruder.  Re-armed system.  Three days later, same PIR, same Intruder Alert at 03:54, no eufy intruder.  Disarm and RearmThree days later, exactly the same process, time 03:55.Three days later, exactly the same process, time 03:57.For the next several weeks I used the remote control to Disarm and then immediately Re-arm the system every two days.  This worked and the system was still active and the neighbors were not inconvenienced. I did then slip-up and missed an off-on session.  The alarm went off at the three day mark again at 03:58.Prior to this holiday the arming of the system was mostly for only a few hours or 24-36 hours. It behaved as expected.
I am puzzled with this behavior, can it be just the PIR?  How can I test it?
I am a reasonably experienced user.  There is now no Comfort installer I can call on.  Any assistance would be appreciated.

Robert    

[slychiu]

Could the alarm be caused by a lizard or spider crawling across the PIR at around the same time on these occasions?  I suggest to add another PIR connected to a spare zone and program the 2 PIRS as Alert zones, ie you need both PIRs to detect motion to trigger an alarm

[RobGG]

I doubt that any lizard or spider could be this regular. I have ordered a new, two stage  PIR and will replace this 2003 relic PIR and see how it goes.
Regards, Robert

[Ian]

I had a spider in a PIR - it was very regular in its habits. It had found a way into the PIR and lived in there coming out to check its webs!