In the current modpack's version of SophisticatedCore, lollipops may cause a backpack from SophisticatedBackpacks to wipe/dupe a large part of the backpack's contents, as shown in this issue: P3pp3rF1y/SophisticatedBackpacks#631
This issue is resolved in the newest version of SophisticatedCore, so maybe upgrading to that version ASAP would be a good idea as to prevent any future progress loss for players using backpacks.

EDIT: Doesn't seem like it's fixed yet, actually

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