I just recently upgraded to 2.2.15 and ever since have been getting a ton or these errors from Google. It does seem the threads giving the errors for my site ate threads that have one or more posts with only media or pictures and no text. I do hope this can be fixed in the next update.
We just yesterday changed our (Google's) Search Console validation so that an image/video will also satisfy the content check. So as long as XenForo is including inline images in the markup (which I think it is) these should disappear shortly.
Though this does still impact the first posts of threads, where we use JSON-LD instead. In any case, as I've commented previously:
1) This is typically a tiny minority of posts (<0.4% of posts on this site)
2) This does not affect the rich result eligibility of other posts in the thread
3) Schema doesnot have any direct impact on ranking, and invalid schema does not hurt ranking