7.3.2 disk keeps spun up?

I have my disks set to spin down after 15 minutes. Since updating to 7.3.2 one of my disks stays spun up, and if I spin it down it just is immediately back up.

inotifywait -mr /mnt/disk4 shows constant access:

/mnt/disk4/ OPEN,ISDIR 

/mnt/disk4/ ACCESS,ISDIR 

/mnt/disk4/ CLOSE_NOWRITE,CLOSE,ISDIR 

/mnt/disk4/ OPEN,ISDIR 

/mnt/disk4/ ACCESS,ISDIR 

/mnt/disk4/ CLOSE_NOWRITE,CLOSE,ISDIR 

fatrace in a privileged docker shows:

# fatrace | grep disk4

emhttpd(7418): RO  /mnt/disk4

emhttpd(7418): C   /mnt/disk4

shfs(10526): RCO /mnt/disk4

emhttpd(7418): RO  /mnt/disk4

emhttpd(7418): C   /mnt/disk4

shfs(10526): RO  /mnt/disk4

shfs(10526): R   /mnt/disk4

shfs(10526): C   /mnt/disk4

emhttpd(7418): RCO /mnt/disk4

shfs(10526): RCO /mnt/disk4

emhttpd(7418): RCO /mnt/disk4

shfs(10526): O   /mnt/disk4

shfs(10526): RC  /mnt/disk4

No access to /mnt/disk1, 2, 3, etc.

Stopping Docker makes no difference

I suspect it is related to the shares set to high-water as disk4 has the most space

Just a data point for anyone else about to update to 7.3.2 to keep an eye out.