Here there is the bug-thread I've opened on github (with a bugmenot account cuz lazy xD):
https://github.com/koreader/koreader/issues/285
Yes, it restarts the framework due to low memory, to avoid crashing itself. The framework now is so heavy, if only it could be shut off while keeping X on... maybe would be useful also to execute debian and other distro flawlessly.
It's quite a shame to have a Kindle PW with a double frequency CPU respect to Kindle 3, but that runs slower due to insufficient RAM...