Is there some reason Civil 3D would force an app into SDI mode

[ronprep]

Our app uses acrxRegisterAppMDIAware and normally there is not an issue with opening multiple drawings and switching between them.  However, some users of Civil 3D with ArcGIS loaded have reported that after loading our app, Civil 3D switched into SDI mode (SDI set to 2 or 3) and it cannot be set back to 0.  

[Norman_Yuan]

According to AutoCAD documentation, when SDI is 2 or 3, there is nothing user can/should do:

normanyuan_0-1734644838922.png

[ronprep]

This is an ObjectARX topic thread, which means I am not inquiring about user interactions but rather why AutoCAD would switch the SDI variable to 2 or 3 forcing it into SDI mode.  As I mentioned, our app uses acrxRegisterAppMDIAware to notify AutoCAD that our app is MDI aware.