The "description" of your coax setup really is not very descriptive. Also is the Velop the only device handing out IP addresses? How about the Airport Extreme, is the DHCP disabled on that?It's been a while since I've been here - good to know lots of people still have MoCA issues.
For the coax cable: Verizon FiOS box -> Filter -> TiVo Premier XL4.
For the internet: Verizon FiOS box -> Ethernet port -> Linksys Velop router -> "wireless here" -> Apple Airport Extreme -> Netgear 5 port switch -> the TiVo (so the TiVo *thinks* it's hard connected via the ethernet port).
My FiOS is a little unique - I do not have any of their equipment inside my house (no Verizon-branded router, etc) - I just have an Ethernet port for router and a cable drop for my TiVo. So there shouldn't be any issues with 2 competing networks, etc.
Near my TiVo is a lot of other AV equipment - Sonos connect, Apple TV, an AV receiver, Blu-ray player, and plasma TV. I'm able to turn off all the equipment save the Apple TV (used for Homekit) and the TiVo in order to save energy.
The TiVo is creating the MoCA network, and I have 2 TiVo Minis. One, located on the same floor, works just fine, with around 99% uptime. The other, located in my basement, seems to work only when it is booted while most of the AV equipment is off. If I try to start the Mini while the other equipment is on, then I get an error that the TiVo is not connected to the internet, and the IP address is a 169. address (self-assigned).
I've tried replacing the coax cable with the shortest one I can find to cut down on any interference, but that hasn't done the trick. Now I'm looking for suggestions.
If the problem is not due to you network connections/router(s) then you might just have a common MoCA issue due to a marginal coax connection. Are you using Verizon supplied splitters, i.e., the Verizon branded ones? Checked all the coax connections to make sure they are tight? And yes in an iffy situation like yours, one trouble shooting step would be to reserve IP address for all tivos in this case on the Velop router, rather than the device.