panic: /e: bad dir ino 584288256 at offset 0: null entry

After running arm64 for a few weeks, sometimes doing something ordinary, eg:

$ ls

or in this specific case

$ lynx http://such-and-such

I get this panic
[ 741378.628740] panic: /e: bad dir ino 584288256 at offset 0: null entry

And I fsck this disk till the cows come home, fsck -yf --- and no errors are reported.

[ 3.086358] sd0: fabricating a geometry
[ 3.086358] sd0: 9314 GB, 9537536 cyl, 64 head, 32 sec, 512 bytes/sect x 19532873728 sectors
[ 3.103183] sd0: fabricating a geometry
[ 3.103183] sd0: GPT GUID: 7dfb7a5f-5343-491b-a518-d9c5641114c8
[ 3.103183] dk0 at sd0: "74b98416-ea2c-4bcd-b591-dcb7844ac861", 19532873661 blocks at 34, type: ffs

Filesystem 1G-blocks Used Avail %Cap Mounted on
/dev/dk2 458 246 188 56% /
/dev/dk1 0 0 0 76% /boot
kernfs 0 0 0 100% /kern
ptyfs 0 0 0 100% /dev/pts
procfs 0 0 0 100% /proc
tmpfs 0 0 0 0% /var/shm
/dev/dk0 9169 3865 4845 44% /e

NetBSD arm64 9.99.69 NetBSD 9.99.69 (GENERIC64) #0: Wed Jul 22 06:15:21 UTC 2020 mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/evbarm/compile/GENERIC64 evbarm

I do not know how to 'tickle' this into panic-ing; but about every 2 weeks-ish, after the console has been idle for a day-ish, doing something innocuous will cause this.

My guess is it's not necessarily something with this particular version of -current, but is something in the disk structure?

Any suggestions on how I can fix this? (I'm happy to try newer kernels, etc).

Thanks, all,
Mike