Hi
What you are saying doesn't make sense. Let me explain and be clear you keep saying
When I select from the combobox, it saves correctly into Excel. (ok so you do a Form Submit and it works as intended)
When I open the edit screen and change any other field, not touching the combo box, it clears the combobox in Excel making it blank.
What does when I change, meaning you select something and save it again and now its empty?
Or when you select something in the UI and it changes and disappears? Which one
Also there is a difference between the first Save and the Next
are you doing a form submit or a patch statement?
Also, there are other things like, the datasource is NOT refreshed, or the OnChange didn't trigger so in fact it doesn't realize there ARE any details to write.
Hence my first original post which covers all the others. What you need to do is
1) have a label on the screen (for testing), in the label, have it grab the items from the one multi-select choice, verify that it SEES that data
Then also post your data here. You need to start sharing the screens, the Form modes, everything, because what i said originally is the answer still. You aren't doing them correctly and have to verify what it sees but also what Mode you are using and exactly what type of patch you are doing.