Struggeling with new Orbi Set

After a couple of years my good old RBR50 Mesh kit died and I purchased a RBK762 as replacement. So I ended putting up the RBR760 at the same place as the RBR50 and swapped the RBS50 with the RBS760. Started all up and

First issue:

The pairing process was painful slow. The RBS760 needed a couple of reboots and often ended up with a sync error. So I carried it closer (and I have a quite small house, 60 square meter... all wooden structure, plaster-walls and glass whool insulation. Some steel studs for dry walls) to the RBR760 to get it synced. Which eventually worked. But weird, as the old setup had absolute no problems with connectivity.

Second issue:

In the kitchen and my office, I had just a mediocre wifi coverage. The Mac showed like 2 out 3 bars and everything felt "slow". So, I bought another satellite and put it up next to the kitchen. Which is also just under the office. It fixed the connection in the kitchen, but still the coverage in the office and bedroom above the kitchen is poor. And i bought another one and put it up in the office. Now my connections are all fine, even though I had to spend significant $$$ to buy two extra satellites, I did not need on my old setup.

Still, I do have problems.

I have a NAS attached to a RBS760 in the stairwell. Trying to up or download a file via SMB share sitting in my office, I get like 4MB/s. If I use the web interface I get like 30MB/s. Which booth are pretty poor. Using the ethernet cable to connect to the satellite and then access the NAS I get like 100MB/s up and download speed. But I could live 30MB/s if it would work. 

 The network is build up like those

            /-------- satellite 1 ----------- NAS

            /

RBR -------------satellite 2 ----------- satellite 3 ------- Macbook

So, obviously the link to the SMB share is not ideal. But I do get 30MBs up or downloading a file via the browser from the NAS. Just SMB and AFS are super slow. 

In addition, both satellite 1 and 3 are on the same upper floor. Satellite 2 and the RBR on the ground floor. I guess it would already help if satellite 3 would connect to satellite 1 or even the RBR.

And yes, I know that some people claim 3 satellites are too many for such a small house and they are too close together. But the coverage without them was just very very poor. 

Actually I am super frustrated by now. After using Orbi products for many years, I am actually considering to replace the whole system.

But before I do that... any tips? Is there any filtering or something done when routing the SMB and AFS request from the Wifi to the ethernet? 

Thanks, Frank

EDIT:// fixed the product