I run a semi vanilla survival server using spigot/paper. Recently updated to 1.12. I have a minigame world and a creative world with multiverse.
If a player spends a long time (somewhere over 1h+) in creative apart from the main survival world they lose their survival inventory when going back into the main world.

Here is also a log of my console if it helps. No idea if related or not. http://prntscr.com/fmnti9

On a related issue i have a post from another player on friends server if it helps you any. http://prntscr.com/fmnsiy

If you need more info i shall try my best to help out.

Lastly thank you for an awesome plugin!! and updates. Free as well.
Thanks.

This is a duplicate of #265. It has been fixed in https://ci.onarandombox.com/job/Multiverse-Inventories/423/