Looks like I've just encountered a minor bug with the Quicktimeline in Quickshow Build 389 under Windows 10.
If you delete an event from the Quicktimeline the usual confirmation box comes up to confirm the deletion, you click ok the event is deleted and the confirmation box comes up a second time, clicking cancel or ok will get rid of it, doesn't appear to do anything harmful.
It doesn't exhibit this behaviour with build 378 as tested on another machine running Windows 10 with this build, I then upgraded it to build 389 and the bug then appeared.
If you delete an event from the Quicktimeline the usual confirmation box comes up to confirm the deletion, you click ok the event is deleted and the confirmation box comes up a second time, clicking cancel or ok will get rid of it, doesn't appear to do anything harmful.
It doesn't exhibit this behaviour with build 378 as tested on another machine running Windows 10 with this build, I then upgraded it to build 389 and the bug then appeared.