I am having this exact problem! Were you able to figure out how to solve this?
yes, well I think it just kind of happened by itself. I ended up doing a system restart on the roku, and i think after a day or two the older videos just started showing up. hope it works for you because i know how irritating it was for me!
Thanks for posting in the Roku Community!
For more information about that channel's features and functionality, you'll want to contact the channel provider support directly to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.
You can reach them here: https://support.google.com/youtube/?hl=en#topic=9257498
Many thanks,
Mary