Been working hard on the last several test suite failures for v6 unlocked
files. Now I've solved almost all of them, which is a big improvement to
my confidence in its (almost) correctness.

Frustratingly, the test suite is still not green after all this work.
There's some kind of intermittent failure related to the sqlite database.
Only seems to happen when the test suite is running, and the error
message is simply "Error" which is making it hard to track down..
