Hurray!!
if you look on the left side of the photo it appears to be missing part of the photo. Is this a development thing, as if the rollers didn't get the chemicals over the entire thing, or is this something blocking the image on the inside?
It's a developer thing. It's pretty common on Polaroids.
First and foremost, make sure the rollers are fastidiously cleaned between every pack. OK, sometimes you can't do that if you're in a real hurry, but you suffer if you don't.
Next, the age of the film has a lot to do with how smoothly the chemicals spread across the emulsion when the pack erupts. Old chemicals don't erupt from the package as cleanly.
Third, temperature has a lot of effect. Cold weather makes the spread more erratic, especially at the beginning to the picture (the part you see the problem.)
Finally, technique in extracting the bundle through the rollers is extremely important. Smooth extraction, something I'm not very good at myself, is very important.
There's a bunch of folks, especially on the emulsion lift areas, who can tell you more than you ever knew existed about all of this.
Michael