It is an Docsys 3.1 Arris G34/AX3000 . It is supposedly compatible with my ISP . My ISP is aware of the model of modem, and the slow speeds .
Back in 1991, I worked for a software-company in Massachusetts, and they had a central “hub” / ‘patch-board”, distributing the internet, to all of the offices on that floor . I learned that it was advisable to have coax from the same spool-of-wire, so that all of the impedances would match .
Here in this neighborhood development, they only replace an underground segment with modern coax, when the segment fails, and there are SOME segments that are “1987”-“fine-nine” old TV-coax, which almost pre-dates, the modern Internet .
I’m wondering if there isn’t an “impedance-mismaach”, from the mix, of old, and new, cabling ?