Answer is red text and says "KaTeX parse error"

[Vladimir-omegacoder]

I'm on Windows 10, and asked a question about matrix multiplication implementation in C++. As a respond I get a bunch of red unformatted text, which says "Parse error: KateX parse error: Expected 'EOF', got '&' at position 3: a &_b & c \ d & e..." when I hover cursor over it. Also I checked the chat with my phone and it dispays just fine. Here's what it looks like: