Internet is constantly dropping with a KPN Box 14

For the last month we experiencing constant internet dropping. We have a KPN Box 12 , we always have 4 4 green lights and the internet is dropping in both wifi and cable in random times. The problem seems to be solved if i shut down he modem and turn it on again, but after a few minutes the issue appears again. I have tried everything that i could think of like reset and factory reset and everything is updated to latest version. I have reached a point that i suspect the issue has to do with the modem. We are really frustrated and if this is not solved we will change internet providers.  Please advise further.