Double check that you have no inherited view that remove ``options`` you set on a field !
If nothing works, add a debugger in the first line of ``get_search_result method`` and enable debug mode in Odoo. When you write something in a many2one field, javascript debugger should pause. If not verify your installation.
This module fixes an Odoo bug in the pop up of search that limit the items quantity
to 160 https://github.com/odoo/odoo/commit/8c3cdce539d87775b59b3f2d5ceb433f995821bf
For that purpose, it makes previously a light ``search`` call, to get all the ids.
This process could make the display of the pop up slow, in case of huge databases.