It happens when using the Wireless Crafting Terminal and you use the feature "Ctrl Click to Craft Missing Items" to craft recources for a recipe.
After using the feature and either confirming or cancelling the crafting plan:
The crafting grid stays empty (where normally the unfinished recipe should be) and the items that should be in it get deleted.

This is honestly quite a severe bug, making it possible to delete valuable items on accident.

NAE2 v. 1.6.4
AE2 UEF v0.56.5
AE2WTLib v1.0.34