My 4660X Roku Ultra just updated to 9.2.0 build 4131-46 yesterday, and now I'm having this problem, also with Pandora. I tried disabling Auto and setting the Resolution to 1080p and Audio to PCM, but that didn't fix it. This isn't the only thread reporting problems like this. It is definitely associate with this update. The box is basically unusable now, because it keeps blacking out during a video or song.
I forgot to mention it on my post, but the same things happen to me on my Premiere+. I do have one suggestion for you, go to Settings > Display type > and change the display from Auto-detect (in my case, it's 4K HDR 30 Hz TV) to 4K 60Hz TV that setting solves all of my problems, you may have to experiment to find a setting that works for you. However, the display setting will eventually revert back to Auto-detect.
I'm beginning to think that there may be issues with Software version 9.2.0 build 4131-XX. I guess all we can do is wait for someone at Roku to acknowledge the issues and then fix them.
Model 4630X-Roku Premiere+
Software version 9.2.0 build 4131-29
As mentioned in an earlier post, the problems seem to occur when you change channels, I can make the problems go away by changing the display type from Auto (4K HDR at 30 Hz) to 4K 60Hz TV, I don't know if this will work for everyone.