@David-TP Is my suggestion that "Smart DHCP option is causing the issue" helpful (please see a few posts above?).

Hi All, Hi @TP-Link, @David-TP - I have encountered the same problem as listed here. My Decos are as following: mode: AP Deco M5 (FW: 1.6.0) - main deco Deco M4R (FW: 1.5.4) Deco M4R (FW: 1.5.4)...