I have a Conklin Duragraph that railroads, skips, quits writing or won't lay a consistent line on high quality 100% cotton or excellent wood pulp paper. Hard starts are frequent. When I try to get the ink flowing again by scribbling on cheap lined filler paper, there is never any problem and it writes just fine. Can anyone offer insight about how to fix this problem? I have never tinkered with a nib before.