PTP650 5.4Ghz Automatically Reducing Transmit Power

I'm curious about the normal behaviour of a PTP650, operating in 5.4Ghz.  
First question...

I have a PTP650 link, under 3 Km's(1.86 mi.) that has been displaying some odd behavior.

The transmit power seems to dial itself down below the maximum transmit power I've set, to a point that impacts it's performance, and I cannot seem to do anything to influence it.  I am not exceeding my EIRP for the region, so it's extremely confusing.

We have other links elsewhere in our network, with the exact setup, and they do not do what this pair of radios seem to be doing.  They stay steady at their maximum transmit power has been limited to.

Has anyone seen this before, know what might cause it, or how to fix it?

Thanks in advance.

Neil,

       What does the ATPC Peer Rx value show for the link? if it's a -50 dbm and the radio only needs to Tx at say 5 dbm to hit that value or be within a db of that it will turn the transmitter down automatically. See the note below about ATPC Peer and Radar Areas.

ATPC Peer Rx Max Power
ATPC maximum receive power level at the remote ODU. In a radar avoidance area this is calculated by the software and cannot be changed. In a non-radar avoidance area this can be set manually.