I was experimenting with instant explosions. I lit a minecart with TNT with an activator rail because I heard the that it creates an instant explosion. It didn't, and then I remembered seeing a YouTube video where the youtuber dropped a minecart with TNT and it immediately exploded. I then tried it. Minecraft froze and then crashed, or close. I didn't know that that was the cause so I tried it again and it crashed once more.

More notes:

• Playing on multiplayer (2 other people)
• Windows 10 PC host (me).
• Repeating command blocks possibly active nearby. (could slow the game down a little?)
• LOTS of redstone / command blocks nearby
• 1 addon on the world. (Link to download here) 
  •  Had 1 active error
• Did not test this anywhere else.