Disappearing "Magic Masks"... Bug or Operator Error?

Magic masks disappear when duplicating the timeline, creating a compound clip, or changing the resolution of the timeline. Any help greatly appreciated.
TIA

If the cached / tracked frames are based on a source that you have changed, than they no longer match. I've written about this many times. Classic operator / user error.

If you are using magic mask in the color page you are getting source from edit page. if you transform or change source in the edit page, the tracking won't work because its no longer in sync. It should be obvious if you understand the image processing pipeline or how this software works.

The only ways I know of are to

a) use proper workflow and work downstream. Meaning you lock the edit you track on color page. if you must duplicate the timeline, right click on the timeline in the media pool and choose from menu duplicate timeline.

b) you apply magic mask inside the a protective container like compound clip. You make a compound clip, open it as timeline, apply magic mask and than work on top of that in the main timeline.

c) you render in place after you have performed tracking in order to back in the tracking

d) you do it in fusion page which sources media pool for clip making it more or less immune to changes in the edit page. At the moment Magic Mask 2 is not including in fusion. Usually it takes some time before feature like that trickles down. Last one took about a version for Magic Mask to get to fusion page and about two version to get to fusion studio.

I think the frame where you make the selection, the reference frames do not get cached and are carried over like qualifiers. So you can rebuild the track and get the same track. The in-between frames that are tracked, get cached or rather stored as images on the disk in their own format. After the project is done you can delete them and if you need to because of reference frames you can rebuild the mask. But while you work the rule is you can do almost anything downstream from the magic mask node and very little upstream because it changes the source and cached frames no longer match the new source. So they need to be re-tracked.

Magic mask is not an edit page tool. It was meant to be used to supplement color grading tools and because the intense nature of tracking and computation its caching frames. To keep the whole thing working its best to stick to expected workflow. Lock in edit. Color grade with assistance of magic mask after it and don't mess with edit. If you need it for rotoscoping, than do either in fusion or using one of the methods I mentioned.

Classic operator / user error.

It should be obvious

right click on the timeline in the media pool and choose from menu duplicate timeline.

b) you apply magic mask inside a protective container like compound clip.

c) you render in place after you have performed tracking in order to back in the tracking

First off, thanks for the detailed reply. Now that you have explained this, yes, it seems obvious, but I never would have known that there is a difference between duplicating the timeline on the edit page and duplicating it in the media pool.

Making the compound clip first makes perfect sense. I will give these techniques a try since I lost all the masking on that edit when I changed the resolution to output a larger thumbnail. Again, not important or urgent, but I would like to re-mask the clips before I archive anyway.

Thanks again for taking the time to deal with this. Much appreciated! Cheers.