Here is your sample back. I think all the problems have been handled with some work-around code. I think all the changes are marked with //added but you may need to do a WinDiff or something to make sure.
One big change was to set some datasource to the combobox so a datasource is available in the style object for user when the droplist is not being shown. What ever is set there probably needs to be consistent with the datasources you want to provide in the currentcellshowingdropdown event.
Also, the Enter key was not working when the next row was the AddNew row. It worked as long as the next row had data.
I used version 2021 to check these things out.