Multiverse: importing inventories from .dat

We have 2 worlds, 1 called 'world' and the other called 'mainWorld'.

When trying to use Multiverse Inventories, joining world from mainWorld clears their inventory in world. The only shares between the two worlds is ender_chest, which works fine.
I thought the inventories were lost for good, and then found them intact in world/players/playerName.dat - it seems Multiverse is loading the inventories from its own .json and .yml files, which regenerate to new blank states every time they are deleted and regenerated.

Is there a way to force multiverse to load from the .dat files instead of the blank .jsons?

Thanks in advance: this is causing a lot of issues with players

 

Bump? :<

This is the contents of my groups.yml:

Code:

# Multiverse-Inventories Groups
 
# To ADD, DELETE, and EDIT groups use the command /mvinv group.
# No support will be given for those who manually edit these groups.
groups:
  default:
    worlds:
    - mainworld_nether
    - mainworld
    shares:
    - all
  main:
    worlds:
    - mainWorld
    - world
    shares:
    - ender_chest