@br00ky 

Can you also share same screenshot, but when all Deco are online: to see, how they connect to each other. 

  @Alexandre. 

Thanks so much for your help. I factory reset them and now it looks like this. It's still disconnecting though. 

  @br00ky 

Other that unusual names for Satellite Deco, which I assume are default names, I see no problem with your Deco mesh setup. On screenshot all devices connect to Main Deco, but that could happen on Deco mesh startup, with time devices should migrate to nearby Satellite Deco.

Satellite Deco going offline could be because they are too far of Main Deco, their WiFi link to Main Deco is weak and drops from time to time. Not the case according to screenshot, both Satellite Deco have good link to Main Deco.

Just to cover everything, open info pages of both Satellite Deco in Deco app and make screenshots of top portion of pages that includes WiFi bands Satellite uses to connect to Main Deco.

Example:

  @br00ky 

Thanks. I'll try this. 

  @br00ky 

My Decos are refusing to keep the mesh together.

Absolute cr@p. What can I do? They are not fit for purpose.