Yes... noone has experienced this issue here this why I couldn't find anything when I searched this forum.
Finally I could resolve the problem but I still dont know what caused as everything worked fine when last time (6 months ago) I played with settings.
I had to delete excisting *.zpkg packages + web_prefix + ZYPKGS files from admin/zy-pkgs folder and after I just followed the tutorial here:
https://forum.nas-central.org/viewtopic ... 49&t=14553
Then I was able to reinstall these packages I mentioned. I still got red error warning but I disabled and reenabled the plugin and they all started to work again.
Same thing happened with "Pulse" (Syncthing) extension.
I had to disable and re-enable it and then it started to work.
I thought Pulse extension has to be updated but when I could log on Pulse (Syncthing) panel then a red update button appeared.
I was afraid if I click on it then Pulse will crush but it didn't. I could update Pulse to the latest Syncthing without a glitch.
So far everything works again.
One thing I noticed.
I use Pulse with my desktop. Even if my desktop is off... NAS no longer goes to sleep with Pulse enabled. I don't quite understand why because there is nothing to sync.