The "force password" function didn't work properly while i had site stats activated in jetpack. The redirect to the password-reset page didn't work. After the login, people landed on the homepage (as intended). After that, if they simply navigated through the site, they got logged off after the first navigation move. If they tried to get into the back office, they got redirected to the login page.
The fix isn't important to me, but I thought i'd let you know because jetpack appears to be quite big.