Hi @BillTNZ
I think 8 is fine. And there is no reason to increase the value without need, as long as there are no problems with your Nextcloud.
I have it set to 8 in my php.ini and the warning disappeared after a reboot of my test server. On my production server with identical configuartion it never appeared in the first place. Also someone else here on the forum reported that the message disappeared when he or she restarted the PHP-FPM service, but it reappeared at a later time. All this and the fact that you already tried higher values than 8 and you still receiving the warning, tells me that this is most likely a bug in Nextcloud.
So as long as there are no “real” issues with your instance, I would recommend to ignore the warning for the time beeing, instead of blindly increasing the value. Maybe you could also create a GitHub issue, if none exists yet, so that the Nextcloud devs are aware about the issue and they can check what is causing this warning.