I had a 40 and a 41 chain; no radar resets between
(1/99x4)x(1/99x4) = 0.163248648% chance of getting two of them back to back. It seems pretty high, but thats all it is when the odds are 1/99.
If you were not to have a chain, it will be 1 in 16744464. With a chain of 40, there is a 40x chance. So if you were to have a chain of 40, the chance of back-to-back shinnies are 1 in 10465.29.