I have problems with TVE streams for channels I can normally watch in YTTV. Seems mostly NBC channels. I try to log on nbc.com/live with both Spectrum and YTTV credentials and got info "Sorry, the live stream for your NBC local station is not available." while on-demand content works.
My it be reason for problems with recording stuff from Channels?
I made a partially log summary. There are errors when dvr could not find codec parameters.
You need a connect, or a quatro, or any OTA HDHR tuner and can add the local channels to your DVR, without any additional subscription.
Are you using some sort of VPN or proxy? Sites like nbc.com have blacklisted all popular VPN ip addresses so you cannot stream via a VPN.
I dont use VPN,but smartDNS. To summarize:
I dont get errors like I had before (e.g. forbidden)
I CAN watch on-demand content on NBC site.
I can watch Syfy with no problems.
Some devices like Apple TV do not have GPS built-in so they cannot locate you. I don't have GPS turned on the server.
So definitely something is going on behind the curtain 
but with such problems with stupid Comcast looks I'm not gonna subscribe for another month
UPDATE:
I have VPN also that works, but would be inconvenient to have dvr server all the time on vpn. If Channels had an API maybe it would be possible to write a script whenever dvr server tries to connect to some specific channels it would make secure connection in terminal.