P: Mask problem after edit in PS

Thank you. I'm happy to send screenshots and more detail, if they want.

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I disagree with Per on this.

The root cause of the problem is the way that rotations and flips are implemented internally. Rather than changing the array of pixels, they simply set an orientation tag indicating the amount of rotation (0, 90, 180, 270) and whether there's mirroring. But when PS edits an image that has non-zero rotation, the saved file will have the pixels physically rotated, recorded with an orientation tag of 0.

LR used to get horribly confused when copying/syncing local adjustments and crops between photos with different orientation tags.  Years ago, Adobe originally marked bug reports about the issue "as designed". So I wrote the Copy Settings plugin as a proof of concept and a long design memo explaining how to properly handle orientation tags. The memo included a comprehensive test suite for Copy/Sync, and I published the test results.  Adobe started fixing some of the occurrences and marked by memo as "planned".

I haven't run the test suit in over two years (it takes a couple hours to run). But I did a quickie test just now, copying a linear gradient (upper-left corner) and a subject mask (the tree trunk) between photos representing all 8 combinations of rotation and mirroring. Pleasant surprise -- they all copied correctly! Sometime in the past two years, this got fixed.  

Similarly, crops now get copied correctly:

I retested the Healing tool, and it still gets the coordinates of the healing wrong, I applied the Heal subtool to the tree trunk in the first photo, and when I copy it to all the other photos, it appears in all different locations except the correction one:

Your example of editing in PS shows that code path hasn't been fixed yet either.

Edit Original will send the image to PS without any edits you have done done in LrC, so the mask will not be included.

However, LrC does not treat Rotate and Flip as edits (IMO it should), they don't even appear in the History panel, and cannot be undone. You have to flip or rotate again to undo.

So what you're seeing is to be expected, and as designed.

If you want LrC edits to be included, use Edit a copy with Lightroom adjustments.