Nifi is not clearing queue

[#1]

Hello,
Please we have been having issues recently
where we discover nifi is not clearing queue.
The que is not going up or going down.
And the ERROR IS: "unable to save flow configuration"

The java version is 11.0.4
Platform: RHEL 8
Nifi: 1.15.3

Please can you kindly look into it.
Thanks.

[#2]

@rafy 
The ERROR shared seems unrelated to the action of emptying a connection queue.
Are you trying to delete a connection or empty a connection queue?
Can you share screenshots of the actions being performed?

Can you collect the full stack trace produced in the nifi-app.log when you perform the action?

Thank you,

Matt