V19 API changes to Leader?

I have some basic code to generate a leader with a block for the contents. This code has been in use for a few years with no issues until V19. This also works in AutoCAD up to 2020

public CadDb.MLeader CreateMleader(string type, ObjectId style, Point3d stPt, Point3d endPt)
{
    CadDb.MLeader mLeader = new CadDb.MLeader();
    mLeader.SetDatabaseDefaults();
    mLeader.MLeaderStyle = style;
    //The line below is throwing an error only in BricsCAD V19:  **Teigha.Runtime.Exception: eNullObjectId**
    mLeader.BlockContentId = new ObjectId()
    .....
    return mLeader;
}

Has anything changed in the API for Transactions or MLeaders?
Im looking to see what could have changed to see if it affects the rest of my code.

Thanks!