For a very specific software application, we maintain a base of machines running fvwm 2.5. To update the menu structure, the fvwm2rc default config file is replaced during the update process performed by a package management system. To enable the new menu structure after an update, the user has to manually perform an action: Restart machine, re-login, restart fvwm. The preferred action is to choose "Window Manager > Restart Fvwm2" since no login is needed then and even the windows survive.

Question: How can I invoke an equivalent action as "Restart Fvwm2" from the command line or the package management system? The following command does not work (neither do similar ones):

fvwm -c "Restart"
[FVWM][SetupICCCM2]: <<ERROR>> another ICCCM 2.0 compliant WM is running, try -replace

"-replace" is no option since one needs to log in again after calling it.