The save button stopped to work. (Save as.. does work)
Can't reproduce working perfectly on Arch @Spectacle 18.08.0.
It is confirmed on KaOS and Manjaro.
Works for me with git master and 18.08. What makes you think it's not working? Does the file not get saved to the location configured in Spectacle's settings? If not, can you reproduce this behavior with a new user account or if you move aside ~/.config/spectaclerc?
I think this happened since 'Quit after save or copy' was not enabled. I was used to have it closed onces saved, my colleague too.