It it turns out it's caused by a conflict with my personal anti-virus program. It is a program that I usually use only in Korea where I live, so I think most of you will have no problem. I'll have to contact the virus program development company. If you were interested, thank you.
Enpass is up to date with appstore and Safari plug-in applied. MacOS is also the latest version. In this situation, if try to login to the Dropbox from the safari during execution, the operating system will expand and restart. I first looked at other issues, but they were still the same symptoms, and me login from safari to the Dropbox, and it went on as normal. Please check the situation.