When downloading files, the captcha appears but 9/10 times it doesn't work correctly by either images changing when they are clicked on or with the traffic signs images it is basically a guess as to which sign to click on as half of the images don't actually register as the correct photo's to the software.

 

I literally just spent 10 minutes trying to download something but it wouldn't work because of this issue.

Sometimes the CAPTCHA changes its behavior, I've noticed. if you read the instructions they do change between different showings so it can change from simply "tick the words" to "tick the words until none are left" and variants thereof.