I have had a few issues with modRana recently. However, this maybe because I have started trying it out a bit more.
@MartinK I have been waiting for you to appear on IRC to ask about them, but I will provide I list here so I don't forget in the meantime.

* Firstly I have experienced the above black screen issue while downloading tiles with the screen locked overnight, if you ssh to device it's the [sgx_misr] at 98% CPU bug; only a reboot will fix this AFAIK.

*Secondly logging tracks seems to fail after 3-4 minutes.

*Lastly tile downloads is still a PITA, I have downloaded 160km "around here", however, when I am offline sections of tiles are missing within the area I downloaded. Re-downloading says that all are found locally.

If I can be any more help debugging this let me know.