THat depends on the server returning the right information, ot doesn't depend on aMule. SO the same happens on eMule or any other ed2k client.
I really have no idea why this happens, but the best tip I can give you is to always use large words (three or more letters) disctinctive of what you are looking for. For example to search for Guns'N'Roses lyrics, search for "guns roses" or "guns roses lyrics", but never for "guns n roses" or "guns n" and such

I hope that helps a little. If you get to know someday why this happens and other such weird stuff about the searching, please tell

Greetings!