Thanks @justindujardin and @ines for looking into this.
To confirm, this is probably the most frequent patterns I have as well:
If you were to click rapidly and leave for tea, when you come back the invalid examples could still be in the queue to send to the server, and you would see the error
Is there an interim code-fix or behaviour change that I can make to avoid this? The entire toolchain becomes brittle because of these specific issues.