Calibre uploaded books being erased

I usually keep my Kindle Oasis in airplane mode and every time I take it out of airplane mode to download a book I’ve purchased, it often times “refreshes” and erases the dozens of books I’ve synced to it from Calibre. Has anyone else experienced this issue & do you know of a fix? It’s not the biggest inconvenience in the world, I can just re-add them… but it does sort of suck if I’m away from home when it happens.