Openfire chatting unexpected behavior

We have used Openfire chatting with Android and iOS applications and all things are working perfectly before, but we are facing some unexpected behavior in chatting right now, like messages are taking more time to send and receive. Our app is live.

I am sharing Openfire server debug and error logs and some screenshots. How can I find out what exactly issue happening with server and what could be the solution to resolve this issue?

Also getting some error log from server.

org.jivesoftware.openfire.nio.ConnectionHandler - Closing connection due to error while processing message: <<iqpresence idid='PZzuN-791=''PZzuN-792 '>type<='cget xmlns='http://jabber.org/protocol/caps'' >hash<query xmlns='jabber:iq:roster'>='</query></iq>sha-1' node='<iqhttp://www.igniterealtime.org/projects/smack 'to ='verlivechat.mingletainment.com' id='56-228034331'=' zUcpnM4/q+DDwIoGAIS6ZXa38LA=type'='/>result</'></iq>presence><iq id='PZzuN-832' type='get'><query xmlns='jabber:iq:roster'></query></iq><r xmlns='urn:xmpp:sm:3'/>

Here are the Android application error logs:

D/XMPP-MYXMPP: connected 
2018-10-26 15:09:05.962 11103-11291/ W/Roster: Roster not loaded while processing Presence Stanza [to=livechat.xxx.com/5m7mtgx4ap,id=rRwJ2-3,type=error,status=online,prio=24,]
2018-10-26 15:09:05.981 11103-11238/ D/XMPP-MYXMPP: login: 1540546745981
2018-10-26 15:09:05.999 11103-11275/ W/AbstractXMPPConnection: Connection XMPPTCPConnection[not-authenticated] (0) closed with error
    java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader.parsePackets(XMPPTCPConnection.java:1032)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader.access$300(XMPPTCPConnection.java:993)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader$1.run(XMPPTCPConnection.java:1009)
        at java.lang.Thread.run(Thread.java:764)