Something on Convio servers prevents page refresh?

I've finally got a line on something that's been driving me crazy on the system today. I've created a Page Builder page that I'm checking in a couple of different browsers and I'm getting the most erratic results as to when my most recent changes actually show up. I can see them instantly when I Preview it out of the admin area, but "outside" browsers don't pick 'em up, and don't and don't... and then suddenly they do! At first I thought it was just taking a long time for my changes to make their way through the back end and get published. But for the last half hour or so I've got the same page open in two different browsers, and in one of them I can see the latest change and in the other I can't. Hit refresh refresh refresh.... doesn't show up. I go in and view source to make sure it's not just a platform issue, and nope, there's the change in one but not in the other no matter how many times I hit refresh. Now it's been 20 minutes or so since the last time I tried, so I just hit refresh and hey presto! voila! change appears!

Is this some kind of load balancing thing? Seems like a rule enforced by a session variable or cookie that says "Thou shalt not refresh within 20 minutes." The way it's behaving is exactly as if a timed cookie had expired in one browser but not in the other. It seems particular to PageBuilder, as well, which I hardly ever use. I've never run into this with event or donation forms. Whatever it is, it sure makes page development more fun and interesting. Had me pulling my hair out all day.