We will need to look into this and get back to you about the erratic tuning behaviour as this seems rather strange. Regarding the DAB images that you are seeing, I believe that we can explain that.
At HF and for frequencies between 240 MHz and 380 MHz, the RSP uses a dual conversion heterodyne architecture. For all other bands it uses a homodyne architecture. All wideband receivers are susceptible to producing spurious images that result from signals mixing with harmonics of the various local oscillators. So for example, if you were using a wideband homodyne receiver at say 30 MHz, a signal at 90 MHz could mix with the 3rd harmonic of the 30 MHz local oscillator and produce a signal 'on-channel', giving the impression that the 90 MHz signal is actually at 30 MHz. With a dual conversion heterodyne architecture, because there are two mixing stages, there are many more possibilities for spurious responses.
The way that we to deal with these responses is twofold. Firstly, we use band filters to attenuate the unwanted signals when you selecting signals well away from the unwanted ones. Secondly, we have tried to select a frequency plan to ensure that these spurious responses are well away from bands that people are likely to be most interested in.
The DAB images that you are seeing are one of these spurious mixing products and the problem is that because the spurious response occurs close to the upper edge of the DAB band the band filter gives relatively little rejection. As a consequence, if the DAB signals in your area are strong, the spurious responses will be easy to see. If this is a problem for you, you can try adding more filtering of the DAB signals at the antenna. Alternatively, we have a new API coming aimed at closing the 380 - 420 MHz 'gap'. This API works by dynamically adjusting the frequency plan and if necessary, we can investigate the feasibility of giving the user a degree of control over this to allow them to move where these spurious responses fall.
Regarding the erratic tuning behaviour, please email email@example.com
directly and we will attempt to get to the bottom of what you are experiencing. When you do so, please let us know what your setup is, i.e. PC configuration, CPU/speed etc and what software you are using (including version numbers)