Resetting the sequence's file numbering worked! (so far). Good catch on that! Thanks again for taking the time.

I hope you do not mind. I tried your tips but now the solved camera isn't even moving. I'm not sure if it's something I'm doing or an uninstall / reinstall C4d situation. I record a 3 min screenshare of my process. Would love if you have a min to check out and see if there's something I'm doing wrong.

Thanks so much. Grateful for the knowledge and the video you put together! Going to try again with your tips in mind.

Also I hadn't previously put in a lens profile and had successful attempts, including with the same camera. But the last several have this same issue with disconnected points and sliding only after the 3d solve.

Uploaded the footage (started uploading sequence first by accident sorry). It's the iPhone 12 pro. I'm not 100% sure on the specs but searching on google came up with - 12 MP sensor (1.4 micron photo sites), 26 mm-equivalent f/1.6-aperture lens, PDAF, OIS. Ultra-wide: 12 MP 1/3.6″ sensor, 13 mm-equivalent (14mm measured) f/2.4-aperture lens

Also found this reddit post - https://www.reddit.com/r/AskPhotography/comments/oebv06/iphone_12_pro_main_camera_sensor_size/

Thanks again!

I create auto tracks, then user tracks, check that they are accurate and stick correctly, and then run the 3d Solver. However, afterwards, the tracks are disconnected from the original points and no longer align. (Separately, sometimes the 3d Solver won't even save the user tracks afterwards, leaving only auto tracks which aren't that great for setting planar constraints).

In this pic, the user tracks are on some of the pieces of green tape.

In this pic (after running the solver), they're disconnected and no longer tracking correctly.
!

Any help would be appreciated!