Hi ForrestS -- Thank you for bringing this to our attention. I have forwarded this over to our On Demand team for further assistance. They will work with Discovery to see if these episodes should be available.
ForrestS -- Discovery has not given us an ETA on when this will be resolved. We'll continue working with them on having the missing episode delivered.
It looks like Discovery Channel has given up on it, probably due to low ratings. The main Discovery Channel does not appear to be carrying the final episode, and instead has moved it to the Science channel on Sunday.
As mentioned, the final episode 5 aired on Science this past Sunday (Feb 11.) Since Science is part of the Preferred package, I don't know if Discovery Networks will make it available through the regular Discovery Channel in some form (OnDemand, DiscoveryGo, etc...)
The original missing episode issue looks to have been resolved. As far as the episode that just aired, we upload the content provided to us by the networks. For more information on how to request channel content, please visit: https://www.xfinity.com/support/cable-tv/channel-availability-faqs/