Unstable connection

[#1]

Anyone else seen this?
I turned the power off to both my BT openreach modem and Netgear WNR1000 router (as instructed by Support). I then turned the modem back on and after about 20  min the  DSL light on the BT modem went solid. I then turned my router on and at the point at which it tries to log in to the internet the dsl light on the modem goes out and the  other lights start to flash. After several hours of flashing the connection came back for another few hours before I lost it again. If I disconnect the router, either by turning off the power to it or by removing the connection to the modem, the dsl light comes back solid only to go out when the connection between the modem and router is re-established.
In case it is the router that is the problem I connected the modem directly to a computer but this also made the dsl light go out. I then turned the computer off and the dsl light came back on but immediately went off again as soon as power was restored to the computer.
(Ticket no: 99989863)

[#2]

That sounds like either a faulty modem or a dodgy Ethernet cable. Have you tried a different cable?

[#3]

Yes, I used a different ethernet cable to connect the computer to the modem.
I have also, since I read your post, tried a different cable from the BT modem to the router.
As soon as a connection is established with the BT modem the dsl light goes out.

[#4]

Almost certainly a faulty modem. You'll need to raise a fault.
https://faults.plus.net/

[#5]

As Jaggies has stated if you can raise a fault and put some availability on there I'll get a engineer booked to replace the modem.

[#6]

As per above, there is already a ticket no. 99989863.
I'm available whenever the engineer can call. Almost always in can ensure access if given an hour's notice.

[#7]

Thanks for that.
I'll get a appointment booked and update you shortly.

[#8]

Thanks. I decided to test if it was the modem by taking it to a friend that also has fibre. Since it didn't work on his line either it seemed it was a safe bet that you were right and it was the modem. I went out and bought an Asus DSL-AC68U modem/router and was up and running again 
The engineer turned up this morning and after some tests agreed it was a fault with the modem and replaced it. So I now have a backup