@Hub24 

What you see in Deco app is not maximum network speed, but current network utilization. According to that screenshot, combined downloading from all devices connected to Deco mesh takes 9.2Mbps (out of, I am assuming, 30-35Mbps Internet link) when you made that screenshot. 

Deco app does not provide information in real time, but with delay. If you start downloading very large file from the Internet, eventually you'll see in Deco app the download speed close to the speed of your Internet link.

Credit card terminals must be different issue. If this is your first WiFi mesh, you may find that some devices may not handle WiFi mesh well. They may have been designed before WiFi mesh was common and can't handle well WiFi mesh specific features.

There may be ways to improve terminals connection to Deco mesh. If you want me to help you with this, I will need more information from you:

1. Credit card terminals, can they run on WiFi5 or do they run on WiFi 2.4 GHz only?

2. Please make screenshot of "Show Map" screen in Deco app and share it here, example:

3. With firmware you listed, E4 should have Connection Preference feature that you might need to use (I'll tell you, how). Please check that you have it, it is described in Part 1 of the following document: How to select a preferred signal source on the Deco App

4. Deco mesh has Guest Network. Do you have it enabled and do you give access to it to guests/visitors of your business?

5. Just to make sure you have all Deco units in sync with their firmware updates, open Update Deco screen in Deco app, make its screenshot and share here, example:

  @Alexandre. 

Many thanks for your detailed reply.

I'ill answer what I can in red

1. Credit card terminals, can they run on WiFi5 or do they run on WiFi 2.4 GHz only? 

• Communication

  4G, Wi-Fi (2.4&5GHz), BT

the terminal brand is Nexgo N96. I can't put in the link 

2. Please make screenshot of "Show Map" screen in Deco app and share it here, example:

3. With firmware you listed, E4 should have Connection Preference feature that you might need to use (I'll tell you, how). Please check that you have it, it is described in Part 1 of the following document: How to select a preferred signal source on the Deco App

That option is not showing on my deco app for E4

4. Deco mesh has Guest Network. Do you have it enabled and do you give access to it to guests/visitors of your business? Yes I have it enabled without a password. The plan was to let staff and our cc machines connect to the password-protected connection

5. Just to make sure you have all Deco units in sync with their firmware updates, open Update Deco screen in Deco app, make its screenshot and share here, example:

  @Wrayman 

Thanks for your help

The ISP says up to 100mpbs on the connection which I know prob has a high contention ratio and I'm lucky to get 1/3 of that speed.

• Is the Deco plugged straight into a fibre optic modem in the wall? Yes, on floor 2 of the building, we have the 1st deco plugged straight into the modem port. We then have an Ethernet cable running from 1st deco downstairs to the 2nd deco.
• Is there an ISP router plugged in between the internet feed to the house and the Deco?I think so as above.
• Are you using any network switches? We then have that 2nd deco plugged into the following TP-Link TL-SF1008D 8-Port 10/100 Mbps Desktop Ethernet Switch/Hub which we have our our tills and credit card machines plugged into the 8 port switch. And the 3rd deco is in the bar area connected via BT I think to the 2nd one
• Have you done any hard-wired speed tests from a PC connected to the main Deco or ISP router? the PC is hardwired to the 8 port switch
• Etc

Apologies for the lack of info from me 

  @Hub24 

Thanks for detailed reply, now I have follow-up questions:

1. Your Deco map shows two Deco nodes. There is Main Deco (behind bar) and Satellite Deco (stage area). Satellite Deco connects to Main Deco with strong WiFi signal, which is good. Update Deco page confirms you have two E4s.

The problem: you said you have three Deco E4 units with one of them connected to Main Deco by Ethernet cable. I don't see that in Deco app. Where is the third Deco E4?

2. You have total of 5 devices connected to Deco mesh according to Deco app, is this how many you do expect to be or some are missing? You have all of them connected to Main Deco. Specifically about terminals, how many do you have and are they (or some of them) located closer to Satellite Deco (stage area) than to Main Deco?

I am trying to figure here if you may be having some of devices and terminals still connected to ISP Router instead of Deco mesh and if they are optimally connected to nearby Deco or not.

3. You said you have Deco Guest Network for credit card terminals and staff. Then, what do you use Deco Main Network for?

The point of that question is to figure which Deco network, Guest or Main, will I focus on tuning with you, and which one is better to have credit card terminals connect to.

3. I think I misread this part of your reply. To clarify, please confirm that you are using:

A) Main Network for cc terminals and staff;

B) Guest Network for visitors.

  @Alexandre. Apologies for the long delay in replying.

i turns out I may have the deco set up incorrectly 

original set up 

Deco #1 connected to router then hardwire out of deco #1 downstairs to #2 unit. Then #3 piggybacking off #2.

Our cctv supplier said the way I had it set up was causing it to loop (I don't know )

New set up 

hardwire from router running downstairs then into deco #1 output from deco #1 connected to TP link port for connection of credit card machine and POS.

then #2 running off #1 in the bar and number #3 upstairs connected to #2

The upload speeds fluctuate between 200kpbs and 10mb (I assume that's always at the lower end until traffic is on the system) 

I hope this explanation makes sense 

  @Hub24 

Thanks for update.

Is everything OK with Deco mesh now, or do you have question/concerns I may be able to help with?