Anyone here using Ubiquiti NanoStation pt to pt wireless access points?

We have a couple here at a couple sites that are 0.4 miles away (per
the access points).

Got a connection set up, works great (replaced a T-1 here). Have an
issue where the wireless acts like it drops twice a day. It's only
down for a minute or two and comes right back up, but devices there get
dropped. It's on about a 12 hour rotation, but it's quite regular.
Devices don't lose uptime, just the wlan seems to drop.

The logs on them don't show anything specific.

Any suggestions?