In case paging discards are high on the cell, there is probability that the page is not sent (1st time and repeatition both). I was just assuming this case. Whereas on following attempts may be the page was transmitted and call was through.
Also I don’t think it is possible that the case described (1st time unsuccessful and second time successful) is happening all the time. It must be happening some of the time. Thatswhy I suspected paging getting lost due to high PCH congestion.
I have observed two such cases where
1) In a high rise building MS was reselecting many cells and was continuously doing Location updates. Overshooting of too distant cells was the cause and even sometimes the MS was going into emergency calls.
2) In case MS sends a channel request, then in the time when the channel request is sent and the status of the MS is not registered as dedicated mode, if a page is sent for the MS it will be lost as MS will not respond and also the network does not know that MS is in dedicated mode.