Redmine

"Data has been updated by another user."

This error message is presented whenever you make an update to a ticket which has been updated by another user. When this occurs all of the comments on the issue are hidden and just your attempted submission is shown. You can resubmit it, but you will continue to receive the error message.

It seriously sucks. Instead of the current behaviour, you should show the new updates in some highlighted fashion, alert the user, and then allow them to submit their update anyway (perhaps with a confirmation).

What do you really expect this work-blocking alert to achieve? If you have spent some time working on the update it can easily be lost (like by force reloading the page, which is required to actually submit an update). Intentionally hiding the updated comments also seems contrary to any goal of this alert - like if someone submitted the same update you would not see it, and after force reloading you may well skip it.