"service ppp restart" fails with a message like :
Stopping PPP profile: sfr.
ppp already running? (pid=460).
I think this is due to the stop part of the ppp rc script merely signalling the service to stop without waiting for it to actually finish (as comments in /etc/rc.subr indicate it should).
The failing restart is instantaneous while ppp.log show that the process can take a relatively long time to terminate :
Jan 23 18:21:15 metropolis ppp: tun0: Phase: Signal 15, terminate.
Jan 23 18:21:46 metropolis ppp: tun0: Phase: PPP Terminated (normal).