This is probably only true for languages with non-standard Latin alphabet. Here's the screen recording.
In this particular case, there seems to be a problem with the letter "İ" (capital "i" in Turkish). Since the task name is "İhsan...", Clickup only finds the result if I use the capital "İ". If I search using all lowercase like "ihsan", it won't find anything. Because it thinks that "i" is the lowercase version of "I". But it's not, in Turkish. Here's how it is.
"ı" ---> "I"
"i" ---> "İ"