Translation in OP isn't clear and most likely OP not entirely sure how the site works so he can't write it precisely what's happening to him. The site hasn't really changed for years in these questions as "flood detected" or captcha, I don't see how these problems occur. 
What I see is weird new posters appearing, like the necroposter on here and /lgbt/, and the schizoposter on /bb/ - also on /bb/ political messages appear.
What I think is someone (or more than one person) tries to stir shit up in order to create user dissatisfaction, and steer users away from the site. Create a problem - then offer a solution.

If there is any reasonable user here who is a regular/old user of the site and who is already familiar with the kinks and quirks of Endchan and who can explain in simple English what's going on, it would be cool.