Do you have a scanner? If so scan one image in so we can see what it looks like.

I've recently have had QA issues with Polaroid 66x pack film. For every 10 packs I have used, up to 3 entire packs have had QA issues and another 2-3 packs have had QA issues in one or two of the individual films. But instead of 'streaks' like you are describing, I've had 'burn' blotches.

Polaroid is pretty good getting me replacement packs, but even the replacement packs had issues and it's quite a pain.

Regards, Art.