Anyone know why this would happen occasionally?

Today I made a change to the factory workbook file to add a drawer slide. The change seemed to be good to go, but a few hours later I noticed the drawer slide had vanished. In the factory database, all the changes I made were gone. 

In the project that I was testing with, the prompt for selecting the drawer slide was now blank and when I redrew the drawer cabinets I was using to test with, they no longer had the slide available.

I checked the Microvellum logs and noticed there were a few users who had entries logged for "The Factory File was modified". 

I have their settings locked down so they cannot modify the Template Spec Groups. However, it seems that if they access the Factory workbook through the project specification groups menu, they can actually modify it in the library.

However, neither user was aware of anything they may have done to trigger this. They don't go into the spreadsheets to make changes, only through the prompt ui's. 

We also don't use project specific factory workbooks. 

Is this some kind of sync issue? They were already in Microvellum when I made the change, so the changes I made to the factory workbook were automatically overwritten when Microvellum/SQL noticed there was a difference in the factory workbooks being used? Is there any way to avoid this in the future? This is now the second or third time this has happened.