I think I'll have to inspect the spools that Robo's using but if I manually attempt to spin it, there appears to be a point in which it sticks... and pushing past this results in a fairly audible click. During printouts, I'm again hearing this periodically as the spool slowly takes out filament. I had this with the spool-in-the-Robo-box and now with the first replacement spool. Is this once-per-revolution sticking some sort of feature to add a little tension to the filament? I was just reading in the R2 section that someone was experiencing some gapping and intermittent extrusion but it could be related. My take on the plastic spool holder is that it probably shouldn't be flat on top. Wouldn't a more circular approach allow the filament to spool off there? One version would be just to replace the existing one except just a rounded top. The second version would be a thin cylindrical sleeve (bearing) that you would put between the existing mount and the spool. Or maybe both is the best answer. Back to the original question though, is the once-per-revolution-sticking a feature?