Update

This morning also the cam with the new firmware went offline. 

Since I'm out and needed to see, I used this trick: I opened the Deco app and looked where it was connected (because I repeat, the cams always appear connected even when they are offline on the TAPO app) and I restarted that DECO. At that point the cam forced the connection to another DECO unit further away and also reappeared online on the TAPO app...

  @__Fabio__ Me too, C425 V1 with latest firmware offline again, and I have the backup hub.

Never had this issue with older firmwares.

One workaround which worked, I was able to reboot the H200 hub and then the C425 connected to it. Why it didn't automatically fall back to the hub, which it's supposed to do?

I noticed that now all the cams have updated to the latest fw. And I have a cam that is offline (the most important one). Really annoying.
The cam always appears to be connected with full signal to the DECO unit. I also tried to restart the DECO unit where the cam is connected and it reconnected to the same one with full signal. So it is not a WIFI problem but I think more of a problem with access to the TP-Link cloud. The same cloud that transmits data to the management app