This error occurs in 42.2 with the most recent systemd update
(systemd-228-25.3.1) and in 42.3 with systemd-228-26.6. It does NOT occur with
systemd-228-25.1 (former 42.2 version). Installing the old version also pulls
in older versions of e.g. udev, so the problem might not be with the systemd
package.

I have some NFS4 shares which I mount with mnt-nfs.automount and mnt-nfs.mount
systemd units. According to systemd defaults, these mounts dismount after some
time of no access (I use the defaults, so I don't know exactly when).

However, with the newer systemd the shares are then no more remounted again, if
another access takes places. Applications trying to access the unmounted shares
hang until I manually do a "systemctl restart mnt-nfs.automount".

The "systemctl status" of both the mount- and automount-units does not give any
hint or error.