I think this is not a bug, it's feature, an accurate simulation of armored gunnery.
However, if your shots are landing to the left of the crosshair, then it's a bug. It should be to the right.
How To Aim a Panzer:
1) Offset: Your sight is to the side of the gun, and aims parallel to it. Make two dotted lines, one from the sight and one from the gun. They should be exactly the same distance apart at point A (your tank) and point B (enemy tank). This is by design and the game replicates it accurately.
Note: Range is vertical only, not horizontal. Range alteration does not aim the barrel left or right to focus on the target like the human eyes do.
2) Sights/Optics: Panzermanner were trained to aim using the sights to account for the offset. The target reticle includes triangles which can be used in estimation of offset as well as target speed.
3) The triangles should point at the ground, and the tip of the main triangle should be pointed at the bottom left of the target: the tread.
4) If you figure the above correctly, then the only variable is range. If you get the range correct, you will hit every time. You have to adjust the range manually using lean left/lean right keys. Close range is 4 (400m), medium range is 6, long range is 8. This is on Gumrak... the max distance on Gumrak is about 1000m, but it's very hard to hit anything moving--or partially behind cover--at that range, at least without wasting ammo.
5) Ballistics and tank roll: if you are on a slope, tilted sideways, your shots will follow a parabolic path perpendicular to the horizon, not perpendicular to your sights.
Here is a link to the Tigerfibel, the Tiger manual. The optics and principles are similar but not exactly the same. The offset is much more wide in the Tiger. However, notice that if your target is a tank, he has a gun and a gunner just like you. If you aim for the gun, you would probably hit the gunner instead....
Gunnery section starts at image #65 on the bottom, page 65 of the manual:
http://www.alanhamby.com/tigerfibel.shtml#
This target has been sighted properly. The range was accurate. The shot resulted in a direct hit to the front of the target: