The information pertaining to this is already provided in the FAQ section next to the captcha. Unfortunately, the nature of these checks aren't something that we can make public. These checks will come up if the system detects suspicious, excessively repetitive or automated activity. These will be dropped once system learns about your behavior.
I can get it check for bot usage abuse, but even 2-5 mins to re-enter is a bit annoying.
That seems a bit of an over exaggeration, the frequency of the captcha is once every 2 hours or once every 30 mins for extreme cases. Based on your logs, you are not doing captcha more frequently than this.
Thanks!