Wifi dropping intermittently

My WiFi drops intermittently throughout the day on various devices. It disconnects then  reconnects minutes later. I recently replaced my old Xfinity modem/router with the newest modem xfi8. I also have 3 first gen pod extenders that have worked well. 
I’ve checked the connection strength in all the devices once my wifi reconnects and it shows all is good. I’ve reset modem, checked connections etc. all seem ok. 
Tech is supposed to come look but what will they do if everything is working. 
My specific question is could the new xfi-8 not be working well with the first gen pod extenders?  I didn’t seem to have this problem with the old router. 
Are there any other things to check before I pay for a tech visit? 
Thanks