This will only work if: WHEN YOU DO /home YOU ARE TELEPORTED TO YOUR OLD COOP ISLAND!

Step 1: Ask another player if you can join their coop island.
Step 2: Ask the owner of the coop if they may now kick you from the coop.
Step 3: Wait 5 minutes.
Step 4: Do /home. You SHOULD be teleported to the island you went to in Step 1.
Step 5: Do /coop leave. It shold say in chat:
There was an internal error when attempting to perform this command.
Step 6: Do /coop leave again. If it says:
You aren't in a party!
then do /newisland. Complete!

Does this work for you? It did for me! Post your thoughts in the comments AND...

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- MichaelRH04