Thanks for posting. You have posted your issue in the Bugs on a stable version section yet v8.0.2 does not exist.
Kindly post (here) your Dolibarr setup environment as suggested in [url]www.dolibarr.org/t/post-guidelines/16873/1 This will greatly help the community in assisting you where possible.
Try disabling the ‘events/agenda’ module and try again. I’m wondering whether it is to do with adding an auto entry in the calendar rather than an issue with the actual status of the order.