Hello again,
I've tested 2.1.1 server on same rpi4, using 2.1.3 client software (is windows 10, I didn't mention it before), same client hardware, same jex collection. Previously I uninstalled and erased all user data.

I'm added following into settings.json (client):

"featureFlag.syncAccurateTimestamps": true,
"featureFlag.syncMultiPut": true,

It took....
It's not working, :joy: it throws error:
Last error: Error. Not allowed: PUT