I have encountered two problems with Chop'N'shaft since I started using it. The first: when Chop'N'Shaft is first activated it full down pans the camera so it is level with the ground. This causes it to exhibit an exacerbated meandering away from dense forest areas, as it will routinely click the farthest way tree(in a grove of multiple trees between the character and the screen). I suggest it should full up pan so that it has the view top down on the character, decreasing the speed at which it might leave a starting area.
The second: I decided to do my tree farming at Draynor Manor since it is consistently devoid of people. This area has a few trees tucked away between other trees which can not be accessed. If one of the inaccessible trees is sighted for harvest Chop'N'Shaft sometimes will continue clicking it, even though it is not capable of being harvested, until it crashes. I have seen it avoid this problem by changing target after a bit, often taking ten plus seconds to switch(it seems that it is most often fixed by an adjacent tree re spawning so it might be the search range for this case should be increased a bit).
