Terminal Services over canopy network

We are running 2 VPN appliances over a canopy network linking two offices. The link is sm to AP-BH AP-sm
At this time no VLan is in use.
The client is running terminal services off of a terminal server at one branch. They are also running an outlook email server.

The customer is complaining that their terminal clients are getting disconnected every so often (once per hour)

We have noticed intermittent receive corrupted data on the BHslave only on any frequency we have tried. APs are 5.7 and BH is 2.4
The rest of the link is rock solid.

They are running 512K on the link that is not congested.
This client was using a 256k leased line without issues and decided to switch to wireless.
Can anyone suggest a cause and solution for the dropping terminal clients?