newnfs pkgng database corruption?

Hi,

on a diskless server, I keep the ports tree and pkgng databases on a newnfs NFSv4 mount. After a bunch of "portmaster -a" runs, the pkgng sqlite database appears to get corrupted. For example, when I try to update an existing port, this happens:

root_at_five:~ # portmaster ports-mgmt/pkg
...
===>   Registering installation for pkg-1.0.11
Installing pkg-1.0.11...pkg: sqlite: database disk image is malformed (pkgdb.c:925)
pkg: sqlite: database disk image is malformed (pkgdb.c:1914)
*** [fake-pkg] Error code 70

I have removed all ports and the pkgng databases and reinstalled, but the corruption seems to return after a few days or weeks of installing and deinstalling ports.

On another system that has a disk, that corruption of the pkgng database has not happened over six months or so. I therefore wonder if storing the sqlite database on an NFS-mount is triggering some sort of bug, either in pkgng or in newnfs. AFAIK, pkgng is using locks on the database quite liberally, could that be where a bug is lurking?

I'm happy to help debug this, but someone would need to let me know what to try.

Thanks,
Lars