I tried searching the keyword "Japan" in the non-aviation board and seems like it recorded no result after October 19 2017 and before July 31 2018 for the keywords. I recall at least some usages of the word "Japan" in some threads in the non-aviation board in this period of time. Is there some problems with the search index system of the site in this period of time?
When the site moved to the GCP last week this error occurred. Unfortunately searching either user posts or threads there is now a gap missing on the dates listed above, if you need to find a topic I suggest you try googling it to find it, I have had to do that myself until this issue is fixed