You miss the point - the rules are always the same, and the disk is always the same.
“Device /dev/sda1 did not match any rules.” means that the file system type could not be determined by udisks. As I said, the problem is timing related and prevents the partition being identified sometimes but we don’t yet know what the cause is.
I have just pushed out another diskmount-osmc update with increased log debugging, please update to get it, then when you see the problem happen again please provide the full system journal with:
sudo journalctl | paste-log
Thanks.