rerange: not the 24hour kind.

What on Earth will stop BH Rerange from happening on a PTP 450i?  We have 3 of these links and they randomly lose their session due to ReRange in error log? I am not speaking of the 24hour key refresh either. 

Will turning off encryption keep this from happening?  What can I do to troubleshoot this problem?  Today we had a 450i go down for 5 minutes due to another BH ReRange.  The link is a solid -55 with high SNR and 256 QAM.  8X 8X link.