Looks like its been miss aligned and got to near the gears. The gearstick should be straight. There is a temptation to bend them, to clear the engine cowling. Above the clip/seal that does not matter to much. below it can cause what you have.
If the dipstick is straight it starts looking a bit dark. Some of the layshafts and the camshft run in bushings. These can become worn. When the do, they seem to fail at an accelerating speed. Thus either the valve timing becomes erratic, due to camshaft movement, bearing in mind its under load from the valve springs much of the time. Or the gearchange with become increasingly loose and may baulk at times. Contrary to what most Heinkel owners seem to think the gearchange should be quite good for a dog box. The gears prefer to run in mesh, than out of it.
The tell tale is what muck is in the oil. If there is fine bronze in it, oh dear, engine strip down time. It is less likely a ball bearing has broken up, but it can happen. The bits on the magnetic drain plug, and around, will be larger.