I am converting hex to a UTF8 string using below line.
var obInstruction = Encoding.UTF8.GetString(ob.Bits);
In the result I got � between every character as shown in the picture below.

Result with UTF32
So I added Replace to the line and changed it to var obInstruction = Encoding.UTF8.GetString(ob.Bits).Replace("�", ""); but � won't go away.
When I tried to replace other characters using Replace work fine but not for �.
What is � and how can I remove it?
In Power query, Text.Clean will remove such strange characters but I am not sure how to do in C#.