Hey,
I've seen somewhere a suggestion of you shouldn't just put wildcard characters in the advanced search Field. But it is important to do, because I can reduce my web request in web scraping from... 160k requests to 20. See if you put a wildcard character in a search Field, it'll show this collumn in the quick band overfiew. And don't get me wrong... it's an amazing feature, but it is broken.
If I do that for every Field, you can see that the number of results is only half as much. Both links for comparison:
https://www.metal-archives.com/search/advanced/searching/bands?bandName=*&genre=*&country=&yearCreationFrom=*&yearCreationTo=*&bandNotes=*&status=&themes=*&location=*&bandLabelName=*#bands 43,601 entries
https://www.metal-archives.com/search/advanced/searching/bands?bandName=&genre=&country=&yearCreationFrom=&yearCreationTo=&bandNotes=&status=&themes=&location=&bandLabelName=#bands 161,075 entries
Now I know it isn't meant to be used this way, but since you don't provide a proper api, thats the only way I see. I actually have also a guess, why that bug might be. You probably use sql (its the most common), and in sql you do String comparisons with LIKE
https://www.w3schools.com/SQL/sql_like.asp. Like can to my knowledge only match to strings, not to null. So if now a band has Fields, which are unknown LIKE doesn't match to them. This theory seems to be confirmed, by the bands , missing being all bands where either the forming year, themes or something else is unknown.
Btw. thanks for the great archival of Data.
Have a nice Day :)