@GregZaaa 

Hi,

Can you think of any electric device in your home that routinely switches on around the time your Powerline network has the problems you described?

Like a heater, fan, pump or something else that is connected via a programmable timer switch or a member of your family waking up and plugging something in?

  @woozle 

Yes, well that was one of my initial thoughts.

Running some home automation with telldus, shelly and zigbee.

But I'm not really seeing the pattern.

The things I mentioned are running other protocols and frequencies and not wired.

Yesterday and today I checked and made some changes.

Disconnected the switch and put an IP cam directly into the PA7020. 

No effect.

The PA7020 seems to be connected to the other ones according to the LEDs.

Also, it is mainly one of the PA's systematically failing, the other one is randomly failing.

  @woozle 

So yesterday I hade a new type of event. 
Every night the boat storage has had issues, yesterday the shed went offline for an hour and the boat storage was ok.

I have not changed anything regarding my home automation, shellys or other things.

So hard to see any logic in this.

  @GregZaaa 

Perhaps the Powerline signal is already marginal at the locations you are seeing the disconnects and the slightest additional interference causes the connection to break up.

Could you please check the "Powerline rate" between the "Core adapter" and each of the two "Remote adapters" by using the tpPLC software? (click on the adapters to change which rate is shown by the arrows)

I know it says something about "300 meters" on the retail boxes of TP-Link Powerline adapters, but I guess that must have been achieved during some lab test. In a typical modern home where many electronic devices are in use the maximum distance that allows for a stable connection could be as little as 20 meters.
 

  @woozle 

A few days of testing.

I have the line rate of about 50+ and 70+ Mbps.
I only see one of the devices from the shed, the core-device.
Shouldn't I see both? 

Line rate tells me it is slow as hell. Right? 
Roundtrips are as below (small packets)

Ping statistics for 198.18.200.13:
    Packets: Sent = 389, Received = 373, Lost = 16 (4% loss),
Approximate round trip times in milli-seconds:
    Minimum = 6ms, Maximum = 1679ms, Average = 153ms

really seems like bad quality in general.

  @GregZaaa 

If the adapter in the shed can't see the adapter in the boat storage, then it means it receives no sufficiently good signal from it to establish a link.

Given the numbers you posted, the signal quality between the adapter in the shed and the core adapter must also be marginal. It is likely that sometimes too many of the data packets sent by one adapter will arrive as broken when received by the other adapter so that a functioning network connection can't be sustained between your monitoring devices and the computer.

As for potential solutions. It's impossible to say whether a different model of Powerline adapters would fare better or not. Different models of TP-Link's Homeplug AV2 Powerline adapters use chips from Broadcom or Qualcomm (Atheros), but I have no information whether one is better than the other.