On another thread pipkin wrote:

'yeah, just disconered that too, now have max fire and still only 90% success rate ... Slider works - drops to 60% ' 

not all items can be updated, i.e. it seems to be just the fighting gear.

Yes, I knew that bit,I think the text says as much, and that any equipment that can be upgraded will be highlighted.

 Perhaps that is Joe's 'problem', its not clear from the post. 

The items in your equipment section of your forge with arrows against them can be upgraded. They are special gear