theres info on the the "panic." Its from 2015 is it solved yet?
What you found is the thread I mentioned. I compiled the build some time ago. The "M" at the end of the version number before the timestamp indicates a manually compiled build. Great that it works for you, but I can't say if the fixes Bilgus mentioned above are included. Hopefully we have a proper fix for the problems on the D2 soon.
I have yet to retry a new build - will probably wipe my rockbox git repo and start from scratch this time. And then probably NOT use a 256GB card as a test this time around.