@Parzuwu Are you testing ping from Satallite Deco to Main Deco on WiFi ? You can test ping by using ethernet cable on Satellite Deco and then start pinging to Main Deco.

@Emon121 On 20 MHz all devices support 1x1 MIMO not 2x2 if you select 40 MHz then devices will use 2x2 MIMO.

@Solla-topee This issue still not resolved and why did you mark it as Recommended Solution? 😑🤔🧐

@Solla-topee My Deco M4 ethernet port also changed from 1000 Mbps to 100 Mbps after electricity came back. Everytime when electricity came back ethernet port speed changed from 1000 Mbps to 100 Mbps...

@Doma2018 You can use Recovery Mode to install the firmware from the link below. 👇 https://www.tp-link.com/us/support/faq/2958/

@Winded My Pleasure 💓