Frequent PPP internet disconnects even after replacement KPN Box 12

This question is to the KPN internet team!!

I’m experiencing frequent short internet interruptions and I’m hoping someone can help me understand whether this points to the fibre/ONT connection or something on the KPN network side.

The problem originally appeared as short freezes of a few seconds during Teams calls. I initially suspected my SuperWifi 2, but testing showed that the local network remained reachable while the internet connection disappeared.

I continuously pinged both my KPN router and an external address. During the interruptions, the router normally remained reachable, while the external connection failed.

KPN support therefore sent me a replacement KPN Box 12. The new modem is running firmware: V12.C.26.04.02

The Wi-Fi performance of the new modem looked very good and my ping over Wi-Fi and cable was stable til I started to face the same issue again few hours after the installation of the new modem. 

Checking the KPN Box 12 logs, I can see that the PPP internet connection is repeatedly going DOWN and reconnecting some seconds later.

Some examples from the log:

22:54:51 | PPP Interface DOWN: Connection terminated
22:55:01 | PPP interface UP: Connection established

22:56:21 | PPP Interface DOWN: Connection terminated
22:56:31 | PPP interface UP: Connection established

During those events, the modem temporarily reports IPv4 as 0.0.0.0, with no DNS servers or delegated IPv6 prefix, and then receives the normal WAN configuration again once PPP reconnects.

The same thing happened again:

23:02:51 | PPP Interface DOWN: Connection terminated
23:03:01 | PPP interface UP: Connection established

And again:

23:10:26 | PPP Interface DOWN: Connection terminated
23:10:36 | PPP interface UP: Connection established

There are several more similar PPP reconnects in the log within approximately one hour.

Because the exact same internet interruption problem continues with a replacement Box 12, while the LAN/Wi-Fi connection itself remains available, I’m wondering whether the problem could be between the Box 12 and the fibre/ONT, or further upstream in the KPN network.

Can KPN please let me know what to do in this case? I need a quick solution, since this is directly affecting our home-office here.

Thanks in advance!