@mr600problems Hi, thank you very much for your feedback. Here is the beta firmware:...

@GuiPoM Hi, have you tried to log into the web UI via http://tplinkdeco.net and manually update the latest firmware: Deco M9 Plus(EU)_V1_1.5.1_210126...

@Jubilado Hi， Have you tried to change the location of these two satellite Deco unis to see if it is always the same Deco that caused the issue? Recently, there is a new firmware version for Deco M5...

@Aiman_94 Hi, here is the latest firmware 1.5.1 for Deco M9 plus V2 and some regions has not added the latest firmware yet:...

@AQuinn Hi, For the primary router, did you mean the main Deco, or there is another wireless router? --if possible, could you please draw a simple picture of your network topology? Would there be any...

@RaduMan Hi, did you mean the manual firmware upgrade tool or the Deco APP?—can I have a picture? If you are already on the 1.5.0 which supported web UI, you could try to update the firmware via web...