when entering (or leaving) the nether, the game freezes on loading terrain

The game won't load at all, the only way i have found to fix it is to sign out of my computer and sign back in, trying to exit Minecraft with alt+f4 or the x button does not work. Entering or leaving the nether does not always freeze the game, it is unclear what causes it, sometimes it'll work just fine, but once it freezes i have to sign out and sign back in.