@NuklearNik 

I see this exact same problem with my XE75 (non-pro) system. The online devices are constantly appearing and disappearing randomly. It's actually infuriating to deal with when trying to find a device in the list. Also, when you look up the "offline" client it will still show it connected to a node so as you said, it isn't actually dropping off the network. Seems like a simple fix seeing as the devices aren't actually offline.

It looks like this has been a bug for some time and I wonder if TP-LINK has any intention of fixing it?

  @cadz Yes. I wonder if it has anything to do with DHCP renewal?  Some devices seem to do it more often than others though. We'll see what the moderators have to say.

  @David-TP 

Any suggestion on how to fix this for an XE75 v1 non-pro model?

  @David-TP The link you supplied is firmware version 1.2.8. I'm running 1.2.9. It downloaded automatically.  The problem I reported also happens on my X55 system. Other people are reporting the offline client problem on various other systems. So, what is actually up with this?

David-TP wrote

  @NuklearNik 

Hi, Thank you very much for the feedback.

I think you could try to install the beta firmware here to see whether it helped:

Optimize The Overall App Experience on Deco XE5300/XE75/XE75 Pro

Best regards.