That sounds all good! You are filling the carts correctly. As long as you are printing with the vent pulled off the cartridge, the ink can leave the cartridges. The vent is the hole not near the clip. The plug should be off when you are printing. If it is not then starvation can occur. If it is off - and you are having starvation issues - then the ink is causing it or it is not compatible with our cartridge.
The 1400 carts we sell are not designed for vacuum filling. That is when you partially fill the syringe with ink and suck the air out with the syringe plugged into the fill hole (no needle attached). After you pull a vacuum by sucking the air out of the cart, you then let the ink replace the vacuum you have formed. Some of our other cartridges can be filled that way. Not the 1400. You will damage them by vacuum filling.
Please contact inkjetcarts about their matte positive hybrid ink and let them know you are having starvation issues. If they believe that their ink is not compatible with our cartridges and/or they have a different type of cartridge for you to use - it will be best that you are using ink and carts from the same supplier so that they can support the solution. They should have a cartridge that has been tested with their own inks.
All of our inks are compatible with each and every one of the cartridge designs we sell. We have gone to great lengths to find cartridges that are so. There is no way for us to know if they are compatible with other hybrid or 3rd party inks.