Man that's frustrating. I've had the same thing happen with a 400 page book where the bubbles showed up after I'd already committed to the press. I always cut my PVA with about 10% water now, and I stir it slow for a good two minutes before I even touch a brush. Thicker glue from the jar just traps air no matter how careful you are with the roller. It's a solid move to thin it, you're not crazy.

Man, I used to be the biggest "just show up in person" guy. Thought all that online stuff was for people who couldn't handle the real deal. Then last year I needed a title transfer and the county website had a chat that literally walked me through the whole thing in 15 minutes while I was eating lunch. Total game changer. Now I always check for the digital route first, even if it feels like cheating.