When watching replay of a program while it is still recording, replay repeatedly buffers, then skips to the end of the recording or live view. I have to back up to where I left off, then after playing a minute or two the same cycle repeats.
What channel? Your issue is with them; not with Roku.
Which app are you having this problem with. I have the same issue using Hulu but the problem didn’t start until the Roku 9.4 update.