Using https://en.wikipedia.org/wiki/Wikipedia as the example article:
If you search for "sr", "srp", "srpski", "српски", "Српски / srpski", "serbian" you don't get Serbian. In fact, I can't get Serbian at all no matter what I search for.
However, if you search for "bah", "bahasa" or anything inbetween, you get Church Slavonic.
are you facing this issue only on English Wikipedia or at any other Wikimedia wikis, because on local https://sr.wikipedia.org/wiki/ when i search serbian i get Европа -> српски correctly.
Are you even supposed to get Serbian when searching on sr.wikipedia.org? Either way, yes, I am facing the same issue on Serbian Wikipedia and German Wikipedia.
Serbian has a known issue with language codes that I thought I fixed but apparently not.
Bahasa apparently means language so it is not surprising it has many matches:
{"languagesearch":{"bjn":"bahasa banjar","cu":"bahasa gereja slavonia","gor":"bahasa hulontalo","id":"bahasa indonesia","ase":"bahasa isyarat amerika","ms":"bahasa melayu","mus":"bahasa muskogee","und":"bahasa tidak dikenal","mul":"bahasa <beberapa bahasa>"}}