Use search function by using single words that occur in the forum but combined as one word in the search term, e.g. "admincontrolpanel". If this word does not exist in the forum and it has 15 or more characters it displays the wrong error message:

The following words in your search query were ignored because they are too common words: admincontrolpanel.
You must specify at least one word to search for. Each word must consist of at least 3 characters and must not contain more than 14 characters excluding wildcards.

Do the same with less than 15 characters, e.g.: "hesheit" and the error message will be correct (not found).

Problem seems to exist for a long time, proven here, but with different problem description.

This error occurs more often in my language (German), since we often have nouns which are a combination of single words.