Drag and dropping a compendium folder into itself causes it to self-destruct.

[FrankIsAtank]

When dropping a folder into itself, it disappears and all its contents appear in the compendium root.

The folder seems to still exist but be invisible, as the associated hidden entity appears to still exist.

This is an issue when moving many items into a folder. Sometimes you may accidentally missclick and grab the folder instead of an item immediately above the folder.

[FrankIsAtank]

Foundry VTT 10 DnD5e 2.1.2 Compendium Folder 2.5.6

[ThunderousLeft]

I have also experienced this issue many times, dragging an item even slightly by mistake causes it to occur. I am running latest stable release for Foundry and the module.