@jeushyun you will need to tag tp-link to get an answer. Apparently they do not monitor these posts and require you to tag them.

@Net1 Who is your ISP?

@IanWaller03 Are you using the deco m5 as your main router? Who is your isp?

@sebastiantruji They could be defective. I would contact Tp-link and speak to them directly and see if they can swap them out. I have one suggestion. Have you tried swapping the primary deco with...

@sebastiantruji Can you please follow the guide below to check that your primary deco is indeed in "access point mode"; Step 1. Launch the Deco app, tap “More” on the bottom right corner, and then...

@SajidG i have just had a look on the tp-link deco e4 FAQ and they recomment trying this below; Case 1: 1. Disable QoS features on the Deco app, set Application Priority as Standard and clear all...