I had this happen the other day too. I spent at least 5 minutes each going through 3 different captchas. The slow fade-in / fade-out thing was new and quite annoying. The images were also quite blurry as well.

I suspect that if you have a machine that is less likely to be fingerprinted uniquely, you have to solve more captcha. In this case, I happened to be using Firefox on Linux with a few privacy related addons running. If they believe you are a bot, because you're not watching their ads, or because you are running a privacy enhanced environment, I suspect their algorithms will slow you down.

It would be interesting to prove this hypothesis. I wonder if you browse with Windows + Chrome + No Ad Blockers, if you get right through the captchas vs. if you use Linux + Firefox + Ad block or maybe even the Tor browser.