Many devices get disconnected

After working well for a while I am getting different devices disconnected from the hub although they have new batteries and present activities from a previous day.

Rebooting the hub and ‘fixing the z-wave network’ wouldn’t help.

Any thoughts ?

Are they really offline or is device health just saying they are? I have turned off device health because it has not report accurately for me.

I have the same issue, reported here: More "unavailable" devices
In my case they are really, really unavailable. Bet ya $$ to donuts this is applicable to the original poster as well.