I've moved this out of the Bugs forum into Discussion, because while there might be a bug here, it seems more likely that the bug is in your code. When filing a bug, please use the template.
When asking for help, please post the code you've tried to use - if there is a problem with your code, we won't be able to see it just from the steps you've listed.
Selection model issues like this almost always relate to not having a unique key for each row in the ListStore. From ModelKeyProvider:
Make sure each item is getting a unique key - the selection model uses that key to decide what is selected. If more than one item have the same key, then more than one item will be selected.
* Gets a non-null key value that maps to this object. Keys must be consistent and
* unique for a given model, as a database primary key would be used.
String getKey(T item);