OK, this might be me, or my PC, but...
If I have on display a non-circular MATZ region where two or more MATZs overlap, for example Boscombe Down/Middle Wallop, or Dishforth/Topcliffe/Leeming, then slowly move the display centre away from the MATZ until the centre of the combined MATZ boundary is just off screen, the boundary vanishes.
MATZ stubs still on screen remain.
It does not matter which screen edge the MATZ is moved off, it happens on all four.
This problem does not happen on circular objects such as the Benson or Odiham MATZs, and I have not observed it with objects other than MATZs.
Could I have discovered a bug on the very first day I try using this application ?