fsck segfaults on rpi3 running 13-stable

While running buildworld on a Pi3 running 13-stable  the machine
panic'd. On restart using the previous kernel fsck failed with a 
segfault, which repeated when the disk was moved to a -current Pi3. 

In single user mode on -current the segfault message is

....
7912408300994173476 BAD I=74682090
4313599915630302063 BAD I=74682090
-4473632163892877928 BAD I=74682090
8068741989830080453 BAD I=74682090
3857159125896022134 BAD I=74682090
-4354179704011695453 BAD I=74682090
7611175298055105740 BAD I=74682090
3985638883347136889 BAD I=74682090
-2495754894521232470 BAD I=74682090
7739654885841380823 BAD I=74682090
INODE CHECK-HASH FAILED I=74999808  OWNER=1842251117 MODE=15044
fsck: /dev/da1s2d: Segmentation fault

I gather this like unlikely to be recoverable, but it would be 
nice to understand what went wrong if possible.

Thanks for reading,

bob prohaska