Originally Posted by
sinc
The only time I've ever seen this is in regards to the nested XREF problem others have mentioned.
In other words, Drawing A is XREF'd as an attachment into Drawing B, then Drawing B is XREF'd into Drawing C. If you open Drawing C, you will see that Drawing A is Attached, and you cannot change it to Overlay. However, if you open Drawing B, you can change Drawing A from Attach to Overlay. Then the next time you open Drawing C, you won't see Drawing A, and will have to XREF it as an Overlay directly into Drawing C.