Well, I'm not sure, I did in one of my posts (to lazy to search).

But I do know this behaviour. Everytime it happens (PM refuses to start again in these cases), I open SFOS's terminal, check if a PM is already running with "ps -aux | grep pure" and kill the running PM-process with "kill -9 [PID]" (well, it's Linux beneath and you're able to do - in contrast to other mobile-OSs ).

The problem seems to be, that PM doesn't quit completele sometimes and keeps running in the background without being noticed by an open "window" (as long you as you don't kill it like mentioned above or restart the device like you did) - the flashing GPS-icon you observed could also be a hint on that.

If you try to start PM again in such case, the "initializing"-screen appears and disappears and PM refuses to start - until killing the "hidden" running PM process or reboot. After that, PM can be started witout any problems.

For me, I think the problem is known, there's a workaround for it (ps & kill or reboot) - so, no more thing to complain about.

It's just one of the slight downsides (which will be hopefully corrected sometimes) of using the only mobile OS which seems to be OK in terms of privacy...