Create Crash: NullPointerException in Minecart Controller or Coupling Renderer

What the log looks like

java\.lang\.NullPointerException: Unexpected error\s+at com\.simibubi\.create\.content\.contraptions\.components\.structureMovement\.train\.
at com\.simibubi\.create\.content\.contraptions\.components\.structureMovement\.train\.capability\.CapabilityMinecartController\.tick
at com\.simibubi\.create\.content\.contraptions\.components\.structureMovement\.train\.CouplingRenderer\.

How to fix it

1. Update the Create mod in your mods folder (and on the server, if playing multiplayer) from v0.3 or v0.3c to the latest available release for your Minecraft 1.16.4/1.16.5 version (such as Create 0.3e for 1.16.4 or Create 0.3.2g with Flywheel for 1.16.5).
2. Make sure you are not running a Minecraft 1.16.3 build of Create (labeled mc1.16.3_v0.3 in the filename or crash log) on a 1.16.4 or 1.16.5 Forge profile if a newer 1.16.4/1.16.5 build is available.
3. If the crash log specifically mentions CouplingRenderer and you have The One Probe installed, update both Create (to at least v0.3a or newer) and The One Probe to resolve the coupling crash.
4. Rejoin the world and test crossing chunk borders or viewing coupled minecarts to verify the crash no longer occurs.

Check your own log