You've found all of those caches. Are you sure you aren't filtering out found caches? The Garmin devices track your finds internally (not by the status in the GPX file). By changing the GC code, it no longer matches the internal list of caches you've found and wouldn't get filtered out, so it would show up again.
Yes, i'm sure my filter is ok. It's set to show alle caches including found caches. They were not on the map when I was searching for them for the first time. Used these in my tests because I knew they failed to show up.