Seems like there's some bug in the recaptcha or proxy processing in SER / CB.
I tested with a fresh set of proxies, setting those proxies (socks proxies) in SER I get the blob captchas all over. Testing the proxies in IE manually with recaptcha sites and google.com/recaptcha, I get regular ones shown.
Tried to enter several times a wrong captcha and still getting the regular ones, removing the proxy I instantly get blobs shown. So seems like the problem is still present which would explain the problem solving recatpcha URL / blob captchas. Seems yesterday's update didn't fix it