I agree that your installation may be suspect. You might try downloading some of your flights and running them through the Flarm Range Analysis tool. The results may point out where you have blind spots due to installation issues. If that doesn't help, an instrument evaluation by Richard at Craggy Aero might be an obvious next step. Your Config file may also have some of the range and altitude settings either too low, or possibly some features are not enabled. I had some problems early on, especially when using an early version of the Configuration tool. Richard looked at the file and set it up correctly. And the issues went away. Of course, some of the appearance/disappearance problems may be from the opposing glider's own installation inadequacies. Flarm has been a great addition to my cockpit, especially with the targets showing on the LX9000.