Plugin and internal server error

Hi,
when i use query monitor my front-page.php get broken. https://prntscr.com/nix70v
Its visible ony for logged in users visitors can see the normal page. Why this happen? I tried to go line by line in my wordpress code and cant find any error in queries etc. I use my started theme which is pretty much bones of wordpress. What can cause this internal server error? (i tried disabling all other plugins). Backend query monitor works normaly and i can check queries.