View Groups - display not stable

[Mike Sierra]

After some 'work' I managed to join my 3 monitors (27" @1920x1080 each) into a view group - thanks to the tutorial of Mark Hargrove! There's an immense advantage when comparing View Groups to a single-window display of 5760x1080: The sidemost displayed objects are no longer distorted!
But...
Somehow the display won't stay stable.
Every now and then (irregular intervals between 5 and approx.30 seconds) the center full-screen-window of P3D becomes black for a moment, the left and right full-screen-windows vanish completely for (maybe) half a second, before the display is re-built again. Is simply looks as if the image 'collapses' and is re-built.
No error message whatsoever!
Nasty enough, but as 'kind of bonus' all sorts of viewing angle, zooming factor, etc. are reset to default at the same moment. No matter, whether I have my TrackIR camera active (included in the exe.xml and dll.xml) or not.
With TrackIR active, P3D even quits responding to TrackIR movement data in the re-built windows, not before a mouse-click into the center window brings back the response of P3D to my head movements.
I can't find out why this perpetual rebuilding-of-view-groups happens, nor what it causes.
System specs are in my signature lines, installed video driver is 378.49, all OS updates installed.
Michael.