Laravel 5.1 random 404 errors

I am using laravel 5.1 framework, I have set up my site using WAMP.
I have handled the errors whoops as it is giving response header except 200 OK.

Now the problem here is, sometimes existing routes [i.e. working the very next moment if I try] return 404 page with response header 200 OK.
I am unable to figure it out that in which case it is returning 404 page.
Note that I have my own 404 page designed which I found in the response.

Can anyone help me with this?

via Chebli Mohamed