Sorry you’re running into this.
It sounds like that Roku device is running into the issue outlined here: Update on 4th Generation Tablo Compatibility with Roku OS 14 - Announcements - TabloTV Community .
The channels without the NN.N format are streaming ones and not affected by this problem.
This workaround may resolve the issue: Roku OS 14 Update - OTA Player Issue and Workaround – Tablo .
In the meantime, we’ll pull this thread into Roku 14 and Live Grid Concerns - Support & Troubleshooting - TabloTV Community which has a lengthy discussion and other tips and tricks that may work.