repeated failure to properly shutdown

[bch <brad.harder%gmail.com@localhost>]

Jul 20 13:53:02 kamloops /netbsd: panic: kernel diagnostic assertion
"bp->b_freelistindex == -1" failed: file
"/usr/src/sys/kern/vfs_bio.c", line 334 double free of buffer?
bp=0xfffffe811c4807e8, b_freelistindex=0
Jul 20 13:53:02 kamloops /netbsd:
Jul 20 13:53:02 kamloops /netbsd: cpu3: Begin traceback...
Jul 20 13:53:02 kamloops /netbsd: vpanic() at netbsd:vpanic+0x140
Jul 20 13:53:02 kamloops /netbsd: cd_play_msf() at netbsd:cd_play_msf
Jul 20 13:53:02 kamloops /netbsd: brelsel() at netbsd:brelsel+0x5f0
Jul 20 13:53:02 kamloops /netbsd: wapbl_discard() at netbsd:wapbl_discard+0x20c
Jul 20 13:53:02 kamloops /netbsd: vclean() at netbsd:vclean+0x2ae
Jul 20 13:53:02 kamloops /netbsd: vgone() at netbsd:vgone+0x4b
Jul 20 13:53:02 kamloops /netbsd: vflush() at netbsd:vflush+0xcb
Jul 20 13:53:02 kamloops /netbsd: tmpfs_unmount() at netbsd:tmpfs_unmount+0x2f
Jul 20 13:53:02 kamloops /netbsd: VFS_UNMOUNT() at netbsd:VFS_UNMOUNT+0x24
Jul 20 13:53:02 kamloops /netbsd: dounmount() at netbsd:dounmount+0xbc
Jul 20 13:53:02 kamloops /netbsd: sys_unmount() at netbsd:sys_unmount+0x150
Jul 20 13:53:02 kamloops /netbsd: syscall() at netbsd:syscall+0x15b
Jul 20 13:53:02 kamloops /netbsd: --- syscall (number 22) ---
Jul 20 13:53:02 kamloops /netbsd: 7b202543ddda:
Jul 20 13:53:02 kamloops /netbsd: cpu3: End traceback...