It seams that it is a very commen issue with furling
system, and may be one that cannot be solved
Ideally, the line path out of the drum should be as Belizesailor said, centered to the height of the drum (looking aside) and exiting with an 90° angle from the rotational axis of the said drum.
Looking from upside, I don't know if the line exit angle is critical and I always wonder if it should be as perpendicular as possible from the drum (or from the boat center line if you prefer), or it has not significant influence.
Based on our experience, the line is usually harder to pull at the beginning of the furling
when the line has not been controlled while unfurling the genoa and was rolled completely as a mess (unevenly) in the drum at this stage.
The more the line is rolled in properly in the drum (while unfurling the genoa), the easier it'll be to furl the genoa afterward.
The trick is to keep a bit of tension when unfurling, the problem is to assess how much of such tension has to be kept...not that obvious.
The line get jammed when you start to pull hard (sometimes with the help of a winch) and that the outside turns of the line are forced inbetween the underside ones in the drum.
One solution we found when things are too hard (normally it should nearly always be possible to pull directly by hand on the line without winching, if you have to do so, something is wrong, and you must not insist), we go at the drum and we turn it by hands the first turns to "unlock" the first layers of line, it then goes free as it should be.
Pardon my poor english
maritime vocabulary, the jamming we see in the drum is the same that happen on a winch when the sheets
overlap and get caught by itself ("surpattage" in french), I guess there is a particular word to describe the situation in english
but could not find the proper translation.
Anyway, I hope it was not too confusing and it helped a bit.