I had the same problem. I deleted Cardinal theme, Cardinal child theme, and Swift plugin.
Put them all back and the save buttons still disappear.
It also says to update my theme:
Cardinal
You have version 2.4.2 installed. Update to 2.4.2.
Swift does not say it is out of date
Swift Framework
Edit
The Swift Framework plugin.
Version 2.0.3 | By Swift Ideas | Visit plugin site | Check for updates
VERY annoying for paste changes… but I can deal with it as long as you can fix it soon with a normal update. I don’t want to delete these all again.