The most liked post shown has 6 likes, but even the last one has 7.
Then I tried to find the three most liked posts by searching ordered by likes, but this did not work either. The results were definitely not the most liked posts. The second result was a small action post which is very unlikely to be one of the most liked posts. Then I noticed that the order was the same as when I chose relevance, most viewed, or latest topic. Example link for search Edit: It seems the posts are always ordered like they appear in the topic.
Yes I think your analysis is correct. We limit results to 50 first posts, so any topic with more than 50 posts will have incorrect ranking if a post after the 50th post has more likes than any in first 50 posts.