OBD sets levels to used from materials without elements

Hi everyone,

When opening one of my files, it sets a lot of the levels to used, without them having any elements on them. These are all the levels from the materials. A quick compress removes the used status from these levels, but when closing and reopening the file they are once more set to used. This is only in one file. Is there any way to turn this of. Below are the settings when checking for level usage.

With kind regards,

Jeroen