To me it sounds more like an ink issue, and the combination of all new pen, feed and cartirdge.
If you have any other fountain pen inks it would be very worth trying them in your Safari, a reliable brand I've used for years is Waterman.
Your problem could just be the fact that everything in your pen is new, and it's an on-going issue that the ink in some cartridges just doesn't want to flow well until the pen has been used and cleaned out repeatedly, then they start to work as designed.
To refill ink cartridges you need to use a blunt needle syringe, the type that is used to refill inkjet printer cartridges.
With new cartridges I will use them up, if possible, then fill and empty them a dozen times over with warm water with dish detergent mixed in. The idea is to reduce the 'oilyness' of the plastic (probably polythene) to the point where ink will flow out of the cartridge.
If that seems too fussy, one easy trick that I have found works, is to take the cartridge out of the pen, find a wooden cocktail stick or match if you have any, then into a small bottle cap add one drop of dish detergent, and add to that tap water.
Dip the cocktail stick into the mixture and drop it into the ink cartridge. One drop should do, maybe two.
Refit the cartridge and test. I have used this idea and it worked for me. Hope that helps.
( You can still return the pen if you still don't get the results you expect, no harm is done to it.
I have six Safaris, all most reliable writers, but they do get better with use and cleaning through.)
Edited by Mike 59, 19 April 2016 - 18:44.