How to remove unicode error?

Question

ASP.NET

Good afternoon, I use asp.net mvc 5.
Rarely and unpredictably when displaying text in the browser window, in some words one letter is replaced by two question marks, for example (Dmitry).
I can’t understand the logic of this bug, it appears on random pages and regardless of whether the text is taken from the database or written by hand in the presentation code.
What could be the problem and how can it be solved?