This assumes that the ISP has a short lived DHCP lease. Comcast Business once tried to charge me to roll my DHCP IP from them. They told me I would have to disconnect my equipment for three weeks for the lease to expire. I told them to go fuck themselves, got a minicipal fiber connection, and never looked back.

With Comcast, if I spoof my router's MAC address, I get a new IP instantly... otherwise it is basically static (residential service).

So does that mean they somehow detect the mac address has come from a new device and roll the ip address to prevent people from doing server kinds of things?

I host servers on my home connection and never had issues (but I do use a dynamic dns service to make sure that I always have the correct IP)

Must be nice! I wonder if OP even has the ability to switch ISPs (here in Texas, limited options)

A) There are a lot of potential hiccups with trying to get a new IP:

- Some ISPs assign statically (odd, but true) meaning you will always get the same public IP

- The DHCP lease time is different for many ISPs: 5min to weeks, meaning you’d have to be offline for at least that long in order to be assigned a new IP when connecting

- Some ISPs lease it to the modem and not the router or anything internal (does not apply to what you said, but another tactic: changing the MAC address)

B) OP asked how to investigate. If getting a new IP dodges the issue and it doesn’t happen again, then there’s basically zero chance that the actual cause will be known

Consumer ISPs don't always refresh IP addresses like that. I have had the same IP address on my home internet for years and was told that I would need to purchase a block of static IPs in order to recieve a new one.