This is just to share experience I faced that problem with hatching. I drew a pulley as in the image above. As you see, there are quite lot of line segments. During drawing, the left most of the hatched blue was overlapped partly. And during selecting those lines, I just simply click without caring of the overlapped line. Then the error shown as in right command line. Hatch failed due to a gap=2 between (98.3, 66.47) and (96.3, 66.47). That actually not because there is gap, but because there is overlapped lines as shown by the image below.
I hope this information will be useful for another users.
Apologize if I put this post wrongly. Admin may move or join to another post if necessary.