I also had this difficulty with the PM feature beginning about the time when the new site software came onboard. After some weeks or months of frustration, I discovered that I never have the problem when I am using the FireFox
browser. You might give it a try if you're not already using it.
"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting 'Holy Shit! What a ride!'" ~Hunter S. Thompson