How can I check the value of an aggregated field without direct access to Solr?
There is a way to do this in Views.

Go to the search index config page (/admin/config/search/search_api/server/MYINDEX/edit) and selected Retrieve result data from Solr.  Then clear all caches a few times to be sure they are really clear.

After that, you can go back to the view and add the aggregated fields as Fields to the display.