We’ve identified that in 4.13+ release MySQL driver changed a bit.
Depends on your DB settings a change in rhodecode.ini is required.
Please consider changing your connection string located in rhodecode.ini to:
sqlalchemy.db1.url = mysql://user:password@127.0.0.1/rhodecode?charset=utf8
OR
sqlalchemy.db1.url = mysql://user:password@127.0.0.1/rhodecode?charset=utf8mb4
This is a know resolution to the problem in the topic.