User seemed successfully upgraded their DB but the Tomcat app failed to load.

Starting Coverity Connect ... com.coverity.ces.launcher.SubsystemLauncher$TomcatDiedException: Process died during startup
[ERROR] Caught at top level: null
See log file for details.
java.io.EOFException
at java.base/java.io.ObjectInputStream$BlockDataInputStream.peekByte(Unknown Source)
at java.base/java.io.ObjectInputStream.readObject0(Unknown Source)
at java.base/java.io.ObjectInputStream.readObject(Unknown Source)
at java.base/java.io.ObjectInputStream.readObject(Unknown Source)
Customer Business Impact: High
Reproduction Steps:
1. Shutdown Coverity Connect
 $cov-im-ctl stop
2. Backup database
 $pg_dump -Fc -h DBHOST -U DBUSER DBNAME > coverity-db.backup
3. Drop database
 $dropdb -h DBHOST -U DBUSER DBNAME
4. Create database
 $createdb -h DBHOST -U DBUSER DBNAME
5. Install new version of Coverity Connect
6. Shutdown Coverity Connect
 $cov-im-ctl stop
7. Restore database
 $pg_restore -h DBHOST -U DBUSER -d DBNAME < coverity-db.backup
8. Start Coverity Connect in maintenance mode
 $cov-im-ctl maint
9. Upgrade database schema
 $cov-admin-db upgrade-schema
10. Start Coverity Connect
 $cov-im-ctl start

The actual steps needed :

1. Shutdown Coverity Connect
 $cov-im-ctl stop
2. Backup database
 $pg_dump -Fc -h DBHOST -U DBUSER DBNAME > coverity-db.backup
3. Drop database
 $dropdb -h DBHOST -U DBUSER DBNAME
4. Create database
 $createdb -h DBHOST -U DBUSER DBNAME
5. Install new version of Coverity Connect
6. Shutdown Coverity Connect
 $cov-im-ctl stop
*NOTE that you need to have a new empty db before restore*
7. (On the newly installed Coverity Connect) Drop database
 $dropdb -h DBHOST -U DBUSER DBNAME
8. Create database
 $createdb -h DBHOST -U DBUSER DBNAME
9. Restore database
 $pg_restore -h DBHOST -U DBUSER -d DBNAME < coverity-db.backup
10. Start Coverity Connect in maintenance mode
 $cov-im-ctl maint
11. Upgrade database schema
 $cov-admin-db upgrade-schema
12. Start Coverity Connect
 $cov-im-ctl start
The session "2.2.2. Upgrading with backup-and-restore on an instance that uses an external database" of the "Coverity Upgrade Guide" is very vague:
Create a new PostgreSQL database into which you will later restore the backup.
In this customer's case, they create a new database while putting the old database with a new DB name. And that caused the upgrade to fail. 

Additional note:
If you are doing an in-place upgrade, there's no need to drop or restore the database. However, it's always a good practice to have a DB backup prior to the upgrade.