My most recent post acted this way and I noticed another submission in GDPR had similar pattern.
When I clicked the post button I had a yellow banner pop-up indicating I needed to correct the errors before I could move on. There were no errors.
When it did post there were two entries of my submission on the dashboard. I have not deleted the second one so that it can be investigated.
Thank you for letting us know about this. I would like to investigate this further. Can you tell me what browser(s) you are both working in, please?