Is there any Method to the Madness of Tactics Trainer Ratings?

The title says it all.  I'm going to use this particular blog to begin collecting tactics whose ratings make no sense to me.  

I'll start with this 1398 problem with a 29.1% pass rate and 49K+ attempts.  We are White.  

I don't know how to put the tactics into the puzzle diagram thing without having to doctor it so the rest are going to be links to the tactic.

Tactic 2:   https://www.chess.com/tactics/192096

This one seems way below a 1948 problem.  The first move is so beyond natural.  And it has a 54.3% pass rate.  

 Tactic 3:  https://www.chess.com/tactics/29452

I've worked a lot on my bad habit of guessing into a tactic and it's improved my rating significantly...I like this tactic because when you calculate to a conclusion, it turns out there are several ways to handle the situation depending on which piece the opponent uses to block with...so at first I thought my solution must be off...but then I realized - hey, everything works after this initial move (I almost never notice that in the tactical puzzles, though I should!)  Also, I think this is underrated for that reason...but I suppose I can see where most people would find the first move easily so this one is up in the air.  

Tactic 4:  https://www.chess.com/tactics/36715   

1938 rating and a 62% pass rate.  I think not.  

Tactic 5:  https://www.chess.com/tactics/37423

I said "beautiful" right after finding it but I still don't think this is difficult enough to be an 1862 problem.  And how does that happen with the 61.2% pass rate.  Does the pass rate involve something I dun't understand...like partially correct or previous versions of the problem...I don't get it.

Tactic 6:  https://www.chess.com/tactics/61220

Okay, how is this even a tactic?  And why in the world is it rated 1498?  And why in the world doesn't it have a 90% pass rate?