This seems to be working on both winter 18 and current version. The button shows in "orange". I could change status and save the record.
Please check the permissions on change request object, and if you are the staff or queue member.
If you want to reopen make sure you change the “state” field as well.
I have try my sandbox as well "Winter 18" and I was able to reopen as well. My save button is Orange. Sorry I could not be much help.