AE Keeps re-analyzing 3D tracker!

That is odd. Are you able to use Create Camera if that button click is the first click you do after it finishes analysing? Does it happen on any clip you try, no matter the movie size / compression codec?

Perhaps reseting the AE prefs might help (either hold down alt/option when launching, or if you don't want to lose your prefs, use the button in general prefs to reveal them, then quit AE and drag the prefs folder somewhere safe). Or making sure you've allocated plenty of memory to AE.

All just guesses of course as I'm not seeing this myself, but then I don't know what version of AE or operating system you're using.

You could also check if anyone else has posted this issue, and report it to Adobe yourself (with that video link, and AE version / OS details) at:

https://adobe-video.uservoice.com/forums/911311-after-effects