This was uncanny, so I had to post a SWAG or two.
Almost to the day, my X50 had run fine for 5 month periods, then it goes into Self-Cal for 30 seconds or so, and is back on it's feet again.
It's always been direct wired, power is good, no other RF or GPS devices, etc. Each time the Self-Cal was when I first started up the car, never while driving around.
This second time the car was in the garage overnight and the temperature was mild, around 54F. The detector had worked fine the night before I parked the car, as there is a speed sign in my neighborhood which it alerted to as usual.
Wild theory #1:
So I started doing some math, I start the car about six or seven times a day or so, over a 5 month period, that's about 1,000 power on cycles. Could it be that after every 1,000th power on cycle the X50 remembers and forces a pre-emptive Self-Cal ?
To shoot holes in this theory, if a board member has a X50 Rev 5, that has gone for years without a Self-Cal, then so much for this idea.
Wild theory #2
Could it be my X50's components just coincidentally take 5 months to drift out of tune far enough that it detects this and does a Self-Cal ?
I guess I will wait and see if 5 months from now, near the middle of October if my X50 Self-Cal's again.