Spark users getting Offline status

Hello.
What we use is version “Openfire 4.6.4, build 2bc37e6” and database “MySQL 8.0.21”. Version of spark used is 2.9.4. Server structure is in vmware with:
→ Linux Centos 8
→ 6 Vcpus
→ 52GB of memory.
The server is backed up daily and with that it is necessary to stop the mysql database and openfire. After finishing the backup, the mysql and openfire database is started.
I noticed that many users have Status “offline” on the server and will only connect again after closing the spark on the user’s computer and connecting again. Due to multiple OFFLINE connections for users who are Online, it becomes very slow when typing to another contact.
Why are users Offline since it could not connect due to openfire being out while it is backing up? Is there any parameter in openfire that can solve?
Why is it slow for users who are online while typing?
If anyone in the group can help me, I appreciate it.

Antonio