And about first test with 2 playlists i found second condition that must be met for exception to occur:
1) AAC encoding used for on-the-fly transcoding during sync
2) I don't disconnect device between syncs.
That is in Auto-Sync Settings 1st playlist checked, Syncronize button clicked, 2nd playlist checked, Syncronize button clicked -> exceptions during updating songs from 1st playlist.
If i check 1st playlist, click Synchronize button, disconnect device, connect device, check 2nd playlist, click Synchronize button - all work ok. But if i don't disconnect device, check 3rd playlist and click Synchronize button - i get exception only for songs in 2nd playlist.
With MP3 and WMA encoders all working ok.