Sorry to hear the technician visit has not resolved your intermittent connection issue. I can see that you're still liaising with my colleague Carley regarding this issue, so I am going to leave you in her very capable hands. Do please keep us updated though.
Having left it a week or so, trying to hope it would settle, I am still seeing the dropouts across the connection. It does not appear to be the router, I still have access within my network; but I have to turn off and on the wifi again on my phones to regain Wifi.
Switched to Modem Mode: 21 May Current set-up: SH3 in Modem Mode - TP Link Archer AX50 in Router Mode - M200 Fibre / Maxit TV - Talk Weekends (Now via the SH3 -which is great in a power cut)