Good morning,
I am taking the liberty of writing because I encounter the same problem, that is to say restarts (sometimes freezes) of my Internet Box Plus. I switched to fiber around mid-April, and immediately experienced random reboots. At the beginning this happened to me about once a week, and lately since the new update almost every 24/48 hours. I tested the solutions proposed on this forum in vain, and I strongly suspect that the problem comes from an instability of the box.
I have the impression that we will have to wait for a new model of router in the hope of having a change.