I've contacted uAvionix about this, and I'm waiting for a reply as I believe it's a SkyEcho2 problem. However, I thought I'd post the issue on here too just in case.
Here's the scenario:
2 aircraft on the ground right next to each other (less than 5m apart).
Both turn on their SkyEcho2 and SkyDemon at about the same time.
One aircraft can see the other on SkyDemon, the other can't.
Both aircraft can see other aircraft on SkyDemon.
The issue is still there once airborne.
It's not a time based issue - waiting does not fix it.
Turning off SkyEcho2 and turning it back on again fixes the issue.
It's not always happening.
A group of 4 aircraft also experienced the same issue in the scenario described above.
Other users have reported the same issue within my group of pilots. All with their own aircraft, SkyEcho2 and SkyDemon.
It does seem to be something to do with the aircraft being very close together when SkyEcho2 and SkyDemon are started up.