Cookies crash all the time, what could be the reason?

Question

ASP.NET

Question:
There is a web application written in ASP.NET MVC, about 50 people use it, no one complains. Except one. His cookies break all the time, you have to approach him, clean cookies and temporary files, the program works fine for a short time, then again.
I sinned about the lack of free disk space, but it has 20GB.
What else could it be? Virus?
What can be done? Reinstall Windows?
I can’t say anything about other browsers, everyone is forced to sit on IE Edge.

Answer 1

As a version - The problem may not just be in the free space, but in the fact that his account does not have the right to write there for some reason. For example, the admin conjured with storing cookies in an unexpected place, and a specific user does not have write access. But in general - details are needed. In what state should the cookies be, in which they are.