I got the save file from Weapon. It's actually the same file as seen in the OP but since this is a PBEM the previous file wouldn't do any good without his opponent's password anyways. It's hard to say exactly what happened but it does seem likely that marginal LOS though trees is the approximate cause. Earlier in the same turn the M18 spots the Tiger moving on two occasions and immediately goes into the firing sequence but the Tiger moves out of LOS before the shot is fired, so there does not seem to be anything wrong with the M18. If you set the camera at view level 2 and place it at the front of the turret on both vehicles then zoom in a little you can see how marginal the lines of sight are. Again, hard to say exactly what happened. Maybe the M18 driver had LOS but the gunner did not. My inclination is to file this in the "**** happens in war" category rather than as a bug. LOS from M18 to Tiger LOS From Tiger to M18