As a consequence of (1), the button does not remove any users in my TCI list below the threshold (not having enough films in common with me). As explained above, none of my 150 best TCIs meet the threshold.
This is odd. I once updated the minimum amount of films required in common from 10% to 25% and it removed a ton of my TCI's (whereas lowering the requirement didn't put them back), while spamming that button both added and removed them.
The 50 TCIs are not selected from users meeting your threshold but from ALL users. I just hit the 50 TCI button once and only 1 user had enough films in common, the other 49 didn't. And the 1 user was outside my 1000 best TCIs. You see that it won't work that way.
Again, this is odd. I had the exact opposite: only two users didn't meet the threshold. Could this problem (and perhaps others) stem from your very low amount of rankings?
http://imgur.com/ULiTBwL
http://imgur.com/wqXEWAr
http://imgur.com/2VOTXvd
Beginning to think that the site was made expecting people to have 250+ rankings. While the PSI's in my case might not be the most accurate when I add a few rankings, they are still very accurate. I still think the best thing to do is to import your rankings, spam the regen button for a minute or two and wait a couple weeks until the majority of the remainder that did not get updated gets fixed through regular use.
The easiest solution for this is for Criticker to standardize a 40% threshold for those with 0-100 rankings (30% 100-200 etc.), because 1) TCI's based on 5 films in common aren't that accurate anyway. Most rankings aren't valid: e.g. the person most closely matching my taste might have missed something I saw in a film and gave it a far lower ranking, was in a different mood, ranked it from memory or didn't like it as much as they thought they did. These things result in a false 1-2 tier difference that has massive significance in a 6 film in common system. A TCI of 1.5 with 500 films in common has much more predictive power than a TCI of 1.2 with 20 films in common, but this isn't taken into account in the current situation. Also, the pool of users available if you have few rankings is still huge. 2) Getting a 40% threshold would to a large extent solve the fluctuation problem. If they apparently can't afford to allow refreshes required for a 10% based system, then they shouldn't maintain a 10% system. One contentious ranking on a 6 film in common basis flips your entire TCI network around.