I got my 2nd replacement of deco e4 3pack, due to random disconnection

-It's a  random disconnection from internet connected to deco wifi using just 1 pack, 2 pack or 3 packs configuration.. all device do not disconnect from deco wifi (note: primary router which deco connected is consistent in ping)

-Same issue with the default firmware and the updated build 20190823

-once dc from internet (steady white LED) from Deco

-All devices are affected 2.4ghz or 5ghz android, ios, windows, 10-30mins interval, there are case only smartphone got DC, and vice versa with desktop/notebook.. once got disconnected randomly internet connectivity gets back 10secs to 2mins interval.

-Tried checking each of three as a main router, same issue..even if its only one deco unit, no mesh active, Tried to connect either of the 2 ethernet ports from deco unit

-DC occurs even 1 device connected

-Tried connecting the deco at all 4 ethernet port from main router (non deco)

-previous setup is ethernet backhauled so there is no reason of faulty ethernet port of main router (non deco)

-operated deco modes under Router and AP, same issue

-factory reset doesn't help, and powercycle

-tried to operate only 2.4Ghz, same issue

-roaming is turned off

-beamforming ON of OFF doesn't help either

Any advice from tplink crew?