Try removing the channel from the Roku home screen by navigating to the channel tile, pressing the * key on your remote and choosing 'Remove channel'. Then restart your device from Settings>System>System restart. Once your player starts up again, add the channel back once more.
If the issue remains unresolved, I'd recommend reaching out to the channel providers directly to report the issue and request additional support. Many channels on the Roku platform are developed and maintained by the channel provider directly, and they'll be able to best assist. If other channels are working correctly, and you only experience this issue on those channels (apps), that is likely an indication that the issue lies within that particular channel. In these cases, the channel provider will need to investigate the issue in order to help resolve it.