Couple of questions Vikki...are you using a syringe to fill thru the screw hole? If so, try not to force the juice in too fast, and leave a little air gap instead of filling completely.
How tight are you making the screw when you replace it? You want it just touching the carto and no tighter. If you tighten it too much it will force the carto out of alignment and cause it to leak.
Here's what I do when my carto floods. Blot the top of the carto with a q-tip or kleenex, then hold the kleenex over the carto's .... and blow to clear the center tube. I also have a long sewing needle I use to keep the center clear by reaming it thru and wiping off the excess.
It's a little bit of a learning curve but you'll get it...and it will be SO worth it