I attemped to edit .PHP files associated with a plugin through the Editor in Dashboard while the plugin was active - all .PHP files associated with that plugin have now been marked 'inactive' and the changes are not being reflected on the site. 

Other material on the Internet indicates that if WP detects an error caused by such an edit, it will automatically mark the .PHP files 'inactive' and operate the site using cached versions of those files. Uninstalling and reinstalling the plugin has been suggested as a solution, but this has not worked for me.

Most of the material I have found is several years old - is anyone aware of a fix that has been discovered recently?