I'd not seen these "off-cuts" of items since old ProTools days, and they used to drive me mad there and I swear I didn't see them for years when using REAPER but recently these things are turning up all over the place:
1)
The Strange Overlap
2)
Fade Area Overlap
3)
On Record Overdub
4)
Overlaying Items With Xfade
After testing #4 I noticed that adding & removing an item to the right actually makes the xfade in the left item change, which seems an indication of confused or corrupt project data:
Look At Xfade On Left When I Delete
One common aspect seems to be that they can disappear if the item 'beneath' is dragged.. and another is that they are usually tricky to select.
In some cases I'm not sure why they are there at all!
If it helps to know, I use the item mix behavior called "Enclosed items replace enclosing items" - although I don't actually understand what that means!
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