spdMerlin shouldn't have any effect on WiFi. Check the router's System Log at the time of the problem for clues as to what's happening.
I don't understand what this means but here you go:
Aug 1 09:44:34 wlceventd: wlceventd_proc_event(486): eth7: Disassoc A4:83:E7:61:1D:C1, status: 0, reason: Disassociated because sending station is leaving (or has left) BSS (8)
Aug 1 09:44:34 wlceventd: wlceventd_proc_event(469): eth7: Deauth_ind A4:83:E7:61:1D:C1, status: 0, reason: Deauthenticated because sending station is leaving (or has left) IBSS or ESS (3)
Aug 1 09:55:22 wlceventd: wlceventd_proc_event(486): eth7: Disassoc 52:37:75:62:09:56, status: 0, reason: Disassociated because sending station is leaving (or has left) BSS (8)
Aug 1 09:55:22 wlceventd: wlceventd_proc_event(469): eth7: Deauth_ind 52:37:75:62:09:56, status: 0, reason: Deauthenticated because sending station is leaving (or has left) IBSS or ESS (3)
Aug 1 09:56:50 wlceventd: wlceventd_proc_event(505): eth7: Auth 52:37:75:62:09:56, status: Successful (0)
Aug 1 09:56:50 wlceventd: wlceventd_proc_event(534): eth7: Assoc 52:37:75:62:09:56, status: Successful (0)
Aug 1 09:57:56 wlceventd: wlceventd_proc_event(505): eth7: Auth A4:83:E7:61:1D:C1, status: Successful (0)
Aug 1 09:57:56 wlceventd: wlceventd_proc_event(534): eth7: Assoc A4:83:E7:61:1D:C1, status: Successful (0)
Aug 1 10:00:51 wlceventd: wlceventd_proc_event(486): eth6: Disassoc FC:B4:E6:31:E2:7E, status: 0, reason: Disassociated because sending station is leaving (or has left) BSS (8)
Aug 1 10:00:51 wlceventd: wlceventd_proc_event(469): eth6: Deauth_ind FC:B4:E6:31:E2:7E, status: 0, reason: Deauthenticated because sending station is leaving (or has left) IBSS or ESS (3)
Aug 1 10:00:56 wlceventd: wlceventd_proc_event(505): eth6: Auth FC:B4:E6:31:E2:7E, status: Successful (0)
Aug 1 10:00:56 wlceventd: wlceventd_proc_event(534): eth6: Assoc FC:B4:E6:31:E2:7E, status: Successful (0)
It seems a bigger problem as I can't toggle on to automatically run speed tests in the amtm interface and can't get it to retain my selection for preferred server. Anyone else had similar problems?