If your bug key is not properly maintained mechanically, you will get very dirty signals, as is shown in the above figures, very easily.
You will notice something is wrong without observing the waveform, because the side tone, for example, sounds very annoying in such cases.
After some cleaning of the dot contact, somewhat better signal is obtained, but the mark/space ratio is not correct, because during the process I touched some of the screws determining the gaps.
The waveform looks acceptable now, but I still do not know how to do it in a reproducible manner.
http://www.vibroplex.com/techdocs/original_bug_adjustments.pdf