Graphing stops after 30 minutes

I have a problem when using the live Graphs function in APM Planner 2.0. I recently tested it with a own compiled version (2015-08-27, Ubuntu 14.04) but I observed this problem for a longer time in older versions (1/2 to 1 year?). Even with precompiled versions.

When I connect my Pixhawk FC (AUAV-X2) via telemetry radio modem, I can display and watch the graphs for about 30 min after the first connect of telemetry. It does not depend on the start up time of APM Planner2.
Even when I disconnect telemetry, the max display time is still about 30 min after the first connect.

After the moment the graphs disappear, the only way to recover from this error is to restart AMP Planner2.
Clearing all selections results in only displaying one graph for less than a second (flash) when selecting a single value.
‘Show Values Under Mouse’ gives an ERR (see pictures)

Thanks, I have raised an issue here