I don't know if this is a Minecraft or Realms issue, but for the last couple of weeks Minecraft will initially look to be lagging (especially evident that the sound stops, but activity can continue).  If I stop at that point and try to get out and save, it may look like it worked, but when restarting you either cannot get back in ("timed out" msg) or if you do get back in, you will be back at the last save point.  It may happen after 15 minutes of play or a couple of hours.  It is not feasible anymore to just exit/save every 15 minutes in hopes of not losing more than this.

Please fix.