I have experienced a bug when I try to change a label of a flyoff by double clicking on the flyoff.  Every letter typed puts a discrete label for each letter in the flyoff view window on the left of the screen.  For example:  The label FOH would create three labels in the flyoff view window of F, FO, and FOH.
I hope this makes sense.

Also seen this, but the odd flyoffs disappear after NWare restarts (after the occasional crash when using Expression Labeller).

I've not seen either of these.  If you can give me a project file an repeatable steps to reproduce it (I know, often easier said than done) we can fix it.