So this is something I've wondered for a bit and have never been able to figure out what I've done.
Every so often I need to pull certain areas from a cut and put them in a new timeline. For awhile making in and out points of what I need and hitting command C&V works fine. Then all of a sudden it stops copying and just keeps pasting a prior copy. No matter how many time I try to copy a new area. If I select everything by hand without in and out points command C&V still work. Only every so often it will start working again a few copy and pastes later.
Do I need to empty a cache or something? Is there a reason why it suddenly stops working?
I suppose you could try deleting the FCP user prefs and rebuild them (just by opening fcp again), otherwise you should really be using your insert and overwrite hot keys instead of copy and paste. Never heard of doing it your way anyway, and one key is faster than using 2, twice.