Perhaps I did not fully understand the questions, as there is missing information. Could you let us know what error you get from the Interface?
Sorry forgot to include the error:
Postevent failed: [-11414] Buffered point does not accept new events
Point ID: 28, Connection ID: 232, User: piadmin, User ID: 1, mode: noreplace
Event time: 8-Mar-17 10:21:39, value: 106.53
Unfortunately, there is no way to change the 'questionable' bit of an event once it's archived, without sending a replacement event with the bit set.
However, the -11414 error should not be encountered when all data sources are buffered with PI Buffer Subsystem. In other words, different instances of PI Buffer Subsystem can exchange ownership of the points and should not lock each other out. If you are seeing this error, then that means the connection which generated the error is not properly configured for buffering. For example, I see in your message that the event came from connection ID 232. I would double-check to make sure that this interface is properly configured for buffering, as it seems it currently is not.
P.S. It's recommended not to use piadmin for connections, as it violates the least-permissions security principle.