Periodically Opera will do a complete restart. Any cookies or anything set during that session will be lost. The problem began with the 70 and is still there. I usually have multiple tabs open, anywhere from 3 to 5, on different sites. The problem happens every day, at least once, sometimes more than once.
The web sites open are anything from email, banks, retailers, doesn't seem to matter what sites are open. Opera is the only application open.
The operating systems is: Mac OSX 10.13.6