Sometimes, Minecraft refuses to load terrain.

To replicate this glitch, create a new Minecraft world in 1.14.2. Then, build a nether portal and go to the Nether. You may see glitched mobs, but that is a seperate bug. Try to go back through the portal. You may get stuck on the loading terrain screen. That is a occurance of the glitch. This glitch can also happen when trying to enter the nether, or even when trying to load a minecraft world. The only way to exit out of the glitch is to force-crash Minecraft via Task Manager.