Tracked enemy tanks at 700-800m switching between visible and invisible

[fxmmauser]

Yesterday was shooting at a Stuart tank between 700-800 my tank was not moving, there was a long shoot out between the two of us, I eventually tracked I might had double tracked him was not sure.

Then suddenly he disappear I only saw his wheels/tracks because there were more near to me than he was, so I thought he had despawned but I keep hearing rounds hitting my tank I did a 360 saw nothing I then looked back to the stu position and there he was again... I tried to keep firing but then he killed me.

There seem that moving my turret periscope around him made him appear and disappear according to the position of where my periscope was aiming.