1. Create an event in Google Calendar with i.e. weekly recurrence.
2. Delete one instance of the recurrence (e.g. xxx the event, choosing "Delete" and then choosing "Only this instance").
3. Synchronize with your phone using MPE.
Now, instead of skipping the recursion on the day you chose, that day actually gets two instances of the event.
I still see no reason why there should be two identical instances on one particular day. One workaround could be to delete the original recurrence on the phone and replace it by two new ones.