Screenshots will only work for sideloaded channels and static content (i.e. screenshots of video will not work). FHD (1920x1080) screenshots also require a 4K capable Roku set to 1080p or 4K UHD display type.
Is this potentially a DRM config issue with the content we're loading into our app or is Roku now outputting the video layer of any content including DRM protected, for a side loaded app?
Ok, on closer examination - some players include the video frame when taking snapshots for side-loaded apps only. This is by design, to facilitate testing/debugging. Notice that a) Frames are captured at low resolution b) This is not a security concern since side-loaded apps are not secured in any way - they are just a zip with "open" source, someone exploring it will find DRM keys etc (do not share your code to strangers, don't hand out the keys to the kingdom!)