We bought an older seal laminator and it would produce those exact bubbles on anything over about 36" wide. In talking to seal, they said the crown had worn off our rollers and they needed to be replaced. We replaced the rollers. No more bubbles.
Not saying that's your issue, but if you have run a lot of material through it, it's something to talk to tech support about. Measure the outside diameters and then the middle and see if the rollers still have a crown in them. Ours were flat, causing the ends to touch and not as much pressure to be applied in the middle. If 10"-12" or so on the left and right are bubble free and the bubbles are mainly in the middle area, then my guess is your rollers are out of adjustment or the crown is gone.
Just something to check. I have no idea if that's your issue, but it's the issue we just went through.