Joomla 3.4 components not showing error?

Question

CMS

Good morning.
They slipped a project with joomla, where I'm like a pig in oranges.
The problem is that there is one component. He had some bugs after switching from php 5 to php 7.
It is very difficult to catch, because. the component does not display errors, but just shows the 404 page. How do I enable error display?
In the main controller of the component, it included php_ini("display_errors",1) and all other moments, before an error in some class, notices are shown, but only suddenly the error falls and 404.
In the server panel, it included showing php errors, to no avail! There are notes, warnings, but only a bug, immediately 404 and no errors.
I'm sitting line by line catching by inserting die("stop") until 404 appears, which means there is an error.
How to fix? Already there are no forces ... to rule all this with his hands.