OS: Linux mint 16 kernel 3.11.0-12-generic
wxHexEditor: 0.22 Beta for Linux
Some times, when inserting bytes, after each insertion, an extra byte is shown to be inserted.
Fortunately these bytes are not actually inserted, if you click below the last row, the "actual last byte" is selected.
To get rid of these bytes it's sufficient to overwrite them (with whatever), and then to simply do "ctrl+z".
If you try to delete them using "deletes selected block" a huge mess happens.