It is not a bug but rather a filter artefact, MP3 is a 20 year old standard designed to carry Radio signals over satellite and DAB connections and was originally voiced (optimised) for 90kb plus and has a sweet spot of around 128kb and was never meant to carry very low bitrate audio, these filtering artefacts increase the lower you go and when you go as low as this these kind of buzzes are frequent especially at starts and ends of files, or where there is padding or a click in the audio file (such as a record scratch).
The Fraunhofer codec included in Cubase is superior to LAME so there is no reason to use the latter in preference to the former. The reason Ogg is better in this case is that it is an evolving standard, they keep changing it, so it has a 20 years on MP3 as far as development goes and has been tested with low bit rates, but for the same reason you usually have to deliver in MP3's, it is nailed down as a standard and unchangeable so an MP3 file made on one device will work on others. Ogg meanwhile cannot guarantee that a file made today will play back correctly on old codecs which makes it unacceptable for manufacturers of consumer electronics.
The alternative is WMA, actually optimised for low bitrates and supported on almost all hardware and software players, Cubase handles that as well.
I converted a few hundred OTR shows for a friend to 32kb MP3's and I am afraid that despite what MP3 encoder I tried all showed the behaviour on some files although I could minimise it in the built in MP3 encoder by choosing a HQM and choosing a bitrate rather than a frequency rate. In the end I just had a short silence at the start and end of every file to get rid of this altogether.
I also found that some hardware MP3 players had a higher tendency to play bursts at beginning of files than most software players, so I made sure there was a short silence at the beginning of each file as well.
For those files I had already converted I found an MP3 editor that works directly on MP3 data rather than decoded audio data, that allowed me to speedily remove tiny bits of the data at the end of converted files without affecting the quality of the rest of the file.