I have to test. Newer linux updates have chaneg udev to run mount in sandbox mode so you can not access it. Had fixed this but maybe a update removed my setting.
/lib/systemd/system/udev.service must look like this# This file is part of systemd.## systemd is free software; you can redistribute it and/or modify it# under the terms of the GNU Lesser General Public License as published by# the Free Software Foundation; either version 2.1 of the License, or# (at your option) any later version.
[Unit]Description=udev Kernel Device ManagerDocumentation=man:systemd-udevd.service(8) man:udev(7)DefaultDependencies=noWants=systemd-udevd-control.socket systemd-udevd-kernel.socketAfter=systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-sysusers.serviceBefore=sysinit.targetConditionPathIsReadWrite=/sys
[Service]Type=notifyOOMScoreAdjust=-1000Sockets=systemd-udevd-control.socket systemd-udevd-kernel.socketRestart=alwaysRestartSec=0ExecStart=/lib/systemd/systemd-udevdKillMode=mixedWatchdogSec=3minTasksMax=infinityMountFlags=slaveMemoryDenyWriteExecute=yesRestrictRealtime=yes
RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
MountFlags must be shared ! Then mounting will work after reboot