I'd say that tactics trainer ratings are the most unstable and unreliable ratings on this site by a long shot. Anyone, if they wanted to, could get a 3000+ tactics rating by manipulating the system:
*using an engine on problems
*skipping problems they don't like (no penalty invoked by chess.com)
*duplicate problems happen all the time - free points, so the more tactics you do, the higher your rating will go, even if you don't improve at all
I wouldn't even try to think about chess TT ratings.
I don't know about rating changes: are they related to a sudden burst or solutions that may be due to the puzzle or something similar appearing somewhere on the site.
But I'm resigned to the fact the ratings themselves and points you get for them are insane. I get 1 point for most solutions that usually require more than 2 moves, then I get 5 points for seeing a very simple, obvious Q&R mate in 1! Then I see a mate in 4, miss the mate in 3, and get penalized 9 points for missing the 3rd move.
Next to finally, the "Start" button, with unprofessional-design, becomes a hint button - even larger and in the same place, so my sensative all-in-one touchpad - where you do left and right clicks on pad, has cost me close to 100 points by asking for hints I never wanted.
Finally, every time I fail I go back and redo it (for no points) until I get it right. Once, after losing 9 points for failing the problem, I redid it (no gained points possible) and when I couldn't find it in the short time, I asked for the hint. I didn't realize that would cost me another 9 points! How can you penalize people when they're not playing to gain points?
Puzzle ratings seem to have changed significantly over the past year. For example check out puzzle #0063591 . The rating is now 1768, while a year ago based on a posting in the comments it was 2002. Pass rate of 39.7% is similar to the pass rate at that time. Wouldn't you expect that with a pass rate of less than 50% the puzzle rating would move up not down? Has chess.com revised the rating system for puzzles? Have overall tactics trainer ratings been pushed down?