The streaming channel 115 may have been withdrawn or cancelled by the provider. The provider can add or remove streaming channels at any time, and Roku has no influence over these changes.
If a channel disappeared and then reappeared, it's conceivable that the provider was experiencing technical difficulties or doing upgrades to their channel, causing it to be offline temporarily.
Regarding your other problems with Roku TVs, I'm sorry to hear you've had a bad experience. If you're encountering specific problems with your Roku TV, I recommend contacting Roku support directly. They might be able to offer troubleshooting advice or a solution to your specific situation.