I hadn’t twigged it only mounts when a program tries to access the FS. df doesn’t count!
I found just before the December update that sometimes playing files you would get an endless spinning circle/hour-glass. After it happened a few times I did some digging and found my windows 10 server would disconnect idle sessions after 15 minutes. And sometimes win10 would not respond to new requests correctly. After OSMC gives up 15 minutes later it starts a new connection which works.
I tried to extend the idle time but it still remained at 15 minutes. CIFS and SMB Timeouts in Windows | Microsoft Learn
I solved the timeout issue by installing “cron-app-osmc”. And told it to run “df” every 15 minutes, by adding to crontab:
*/15 * * * * df >/dev/null 2>&1
** update **
I found the following in /usr/share/kodi/system/advancedsettings.xml
30
So I changed it to 0 in /home/osmc/.kodi/userdata/advancedsettings.xml
Removed the contab few days ago and had no issues.