I have tested this fix (in version 4.0.2) as follows:
I created a new event for August 30 at 7:00 pm. I selected to repeat using custom dates. I selected August 31 and Sept 1 as the custom dates and clicked publish. All three events were created correctly. (Including having the venue assigned for all events.)
Then I chose to edit the first (August 30) event. I changed the start time to 6:00 pm and clicked update. When asked, I left the selection on “this occurrence only”. All three events had heir start time changed to 6:00 pm.
I again chose to edit the first event. I changed the start time to 3:00 pm and clicked update. This time I clicked on “all occurrences” and then back on “this occurrence only”. Again all three events had their start time changed to 3:00 pm.
So, editing just the first of a custom date repeating event no longer deleted the repeat events. That issue is fixed. However when editing the original event, the ‘this occurrence only” option seems to be ignored and all occurrences get changed instead.