The idler arm for the Tiger 1 was slightly changed in January 1944 [1] . The original design had a bump on top (to indicate the angle of the arm.) This is reproduced in the kit at 'A'.
In January 1944 this bump was replaced by a lubrication tap. In 1/35 scale, this makes no appreciable difference. But at the same time, another lubrication tap was added near the bottom of the arm. Dragon have now put this in their tooling, at 'B'.
For a vehicle built before January 1944, you should cut off the lump at 'B' if it is present in your kit.