I have the exact same problem with my Deco X50 particularly on the 2.4Ghz band... my video doorbell can't even stream video and my other cameras are constantly going offline and online. I also...

The first two was bought from a retail store: https://shopee.ph/Tp-Link-Deco-M4-2-pack-AC1200-Whole-Home-Mesh-Wi-Fi-System-i.6562415.2726707742 And the last one was bought from an individual seller...

I have a 2-pack Deco M4 initially installed and I updated the firmware to the latest one 2 days ago (1.5.0 Build 20210511 Rel. 34580) Today, I bought another M4 unit and installed it as a new...