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We are currently working on a fix for this issue! Thank you for letting us know!
It's not possible to migrate that data easily, so we won't be able to move unlocks from test to live unfortunately.
The Book of Monsters is a test case for us at the moment, but the long term plan is to make the mastery unlocks persistent across Prestige even, so once unlocked they remain unlocked. They might still receive another reset during Early Access however at one point, but more on that in the future. :)
