Debugging Joomla 4 components - how?

Question

Joomla

It costs Joomla 4.0.3
There is a 1-n component, which is similar in complexity to VirtueMart 3
A situation has arisen:
Created a 1-menu item that should open the user's page (if he is logged in) or offer registration (if he is not authorized).
And it behaves like this:
The link, technically (in the admin panel if you look at it) looks like this: /index.php?option=com_market&view=vendor&layout=form
when you try to navigate the site redirects to /index.php without messages (debugging is enabled and PHP error output is maximum ). Actually a question: how to debug similar? (how to approach this problem)?