Hi Reuben -
Sorry for the trouble. Unfortunately last week GQueues experienced some issues with the calendar syncing processes. This is not related to any changes made to the Google Calendar API, but rather GQueues internal syncing code. In the process of resolving the syncing issues, for some accounts, duplicates copies of tasks were made on Google Calendar. The integrity of the GQueues task data itself is fine, but multiple calendar events were created for a single GQueues task, in some cases.
The syncing issues have been resolved, and we have rolled out a process to fix the duplicates. A notice appears in GQueues upon login for the accounts that may have experienced this duplicates issue, prompting them to run the "fix" process.
In terms of the "Hide Completed" issues you experienced, when you check that box and click Save the completed tasks are not hidden on your calendar instantaneously. Each completed task is processed and hidden from the calendar individually, so this can take several minutes if you have a large number of completed tasks.
If you checked the box to "hide completed" and clicked save, and then unchecked it and clicked save, and then clicked it again this would kick off 3 processes running in the background and they would most likely overwrite each other - so the results could be unexpected, with some completed tasks hidden and others not.
We have put safety measures in place now that will prevent a person from changing this setting while a previous process is still running for the account.
If you still have completed tasks visible on your calendar I would suggest you uncheck the box, click save, wait until that process has completed (usually less than 10 minutes), and then go back and check the box to "hide completed" and click save. After 10 minutes are so all of your completed tasks should be hidden from your calendar.
Sorry again for the extra hassle and time this has cost you.
-Cameron