Reflection problem?

We setup a 2.5 mile link using 2 Tranzeo TR-6000 AP's with integrated 15 dbi in a rural location.

AP 1 18 ft agl AP 2 24 ft agl

There is one tree partially blocking line of site 75 feet from AP 1. A couple of buildings at about the half way point that definately come in to play. Otherwise it is wide open.

So we know this setup has fresnel issues but thought we would give it a try anyway. When the radios are dialed up to full power 23db the throughput of the radios is virtually useless. If we dial the power output on AP 1 down to 18db the link works great. I'm assuming that we are getting a reflection that is causing a high error rate and reducing the power output reduces the strength of the reflection.

Is this typical of a reflection problem? Could the tree be the source of the reflection or does a tree pretty much only absorb? Can a reflection off the ground cause this type of behaviour?

This is not a critical must be up connection, so I'll leave it for now since it has been working good for a month.What are the odds, if nothing else changes, of this link continuing to function reasonably well?

Any input is much appreciated.

Ian