C7100V goes down once a week

Just to preface, I try to be tech savvy but have no experience with networking. Assume I have no base knowledge and explain like I'm five.

I have a Netgear C7100V modem/router running firmware V2.01.33, not sure if its up to date.

I just moved into my brother's house and needed internet in my bedroom. Instead of running an ethernet cable thru the attic I moved the modem to my room and purchased a Nighthawk X6S wifi extender to get wifi thru the rest of the house.

Now, once a week the internet goes down. Not just the wifi, my ethernet connection doesn't work either. I am even unable to connect to the Netgear Genie. Every time I try to reboot it by unplugging the cord it comes back on with a steady red light on the modem (I think I saw that it's due to interrupted firmware update but I could be wrong). After the red light comes on I have to do a 30-30-30 reset, connect to Netgear Genie, reset the password, then the internet magically works. 

This problem only started since I moved the modem and added an extender.

Since it seems to happen every Tuesday I thought maybe my ISP was changing my IP address and the modem wasn't keeping up. I just don't understand why it would happen now or what I could do to check my theory. It also seemed weird to me that I couldn't connect to the Netgear Genie. I don't know what it means but it seems important.

Like I said, I have no knowledge of modems so please explain everything very simply.

-Jordan