CloudLinux is the base operating system with MySQL Governor installed and suddenly a user's max_user_connections gets set to 30.
This is by design. When a user's LVE CPU limit reaches 400, MySQL Governor tries to throttle down the user by setting a low max_user_connections setting.
You can check the users setting using a SQL command like this one as root.
mysql -e "SELECT max_user_connections FROM mysql.user WHERE user='cpaneluser';"
If the setting is at 30 then it was MySQL Governor that made this change.
The log file /var/log/dbgovernor-restrict.log would show the user being limited as well.
You can also use lveinfo to see the users' limits being reached for CPU with
lveinfo --period=1d --by-fault=mem --display-username --user=cpaneluser
There are two options. The first is to disable "abusers" in the MySQL Governor settings or the user can be set to a higher CPU threshold. This is an example of setting the CPU to 800 instead of 400.
dbctl set cpaneluser --cpu=800,380,350,300