Syncthing is blocked, or better the ports are blocked on 3 of the hosts (and i cant open them). I can use scp, to copy files. Ports 22 and 443 are the only ports, i can use on all hosts. Additionally, i cant install new software there.

For the restart, i have found the line exec "$(realpath $0)" "$@". Using the script directly works with that. But since the script is called from a systemd service unit, i don't know if this break the logic. The service unit is from type oneshot and calls the script multiple times (but different parameters), like this:

ExecStart=/home/username/.local/bin/script.sh variant1
ExecStart=/home/username/.local/bin/script.sh variant2
ExecStart=/home/username/.local/bin/script.sh variant3

script.sh does different things, when changing the first parameter. It starts the other variants, when the current variant finishes. Now i don't know, if restarting /home/username/.local/bin/script.sh variant1 will break the logic and the other variants will either not executed or in some unexpected schedule.