Drum Editor strange behaviour

When I “write in” a percussion pattern all goes well until I either try to delete a hit or move a hit by dragging - then everything goes haywire, the rest of the drum pattern will shift a beat “forward”.

I entered a hi hat pattern and reduced the velocity (with the pencil) of every other hit - which MUTED every other hit. When I select and delete the hi hat hits to try again the WHOLE PATTERN disappears as though I’ve “Selected All”. “Undo” just takes me back to the previous mess. If I “Undo” enough times I can get everything back on the grid as it was before I started editing but then it starts all over again HELP!

Windows 7 64-bit, Cubase 64-bit 7.5.20, BFD3 latest version.

It happens with the GM drum map or “drum map from instrument”.