How to release process model sequence file object?

Question

Calling engine's method GetStationModelSequenceFile we get the reference to the process model sequence file object. According to TestStand Help, you should "Release this reference when you are done using it." The question is: how do you release it? Call engine's method ReleaseSequenceFileEx passing the reference to the model sequence file gotten from GetStationModelSequenceFile won't work, it returns FALSE which means the sequence file can't be released. Similar problems exist with methods SequenceFile.GetModelSequenceFile, Execution.GetModelSequenceFile. My aplication is written in VB. Using the statement like
Set modelSequenceFile = Nothing also does not solve the problem.  I want to get some information of process model, such as version number, so I call those API functions in my code, which was developed under TestStand 3.1. I post this question because when I ran my application with TestStand 3.5 or 4.0 beta, I got the warning dialog when loading a sequence file and then closing the application. The dialog listed all the unreleased objects which I figured out is due to that the process model file was not released. Because message in the dialog is as following:
The following top-level objects were not released:
        Sequences [1 object(s) not released]
            Sequence #1:
                Name: Test UUTs
        Type Definitions [43 object(s) not released]
            Type Definition #1:
                Name: TimeDetails
            Type Definition #2:
                Name: ReportOptions
Of course there are more in the list, but the sequence file loaded into the application is released correctly by calling engine's method ReleaseSequenceFileEx, so it does not appear in the list.
Any help will be greatly appreciated.

Answer 1

Here are what I did after launch the operator interface:
1) Call Engine.GetSequenceFileEx to get a reference to a sequence file.
2) Display steps of MainSequence of the sequence file in GUI.
3) Call Engine.GetStationModelSequenceFile to get a reference to the station process model sequence file. The variable used to save the reference of process model sequence file is modelSequenceFile.
4) Loop through all the sequences in process model sequence file, get the references of entrypoint sequences in the process model and put them in a container (VB Collection).
At this point,
Calling modelSequenceFile.CanUnload returns TRUE
Calling modelSequenceFile.IsExecuting returns FALSE
Calling Engine.ReleaseSequenceFileEx(modelSequenceFile, ReleaseSeqFile_UnloadFile) returns FALSE
There is no other loaded process model sequence file reference at this point.