scan doesn’t stop

Can you enable debugging in WordPress and see if there’s anything written to the PHP error log:
1. Edit your wp-config.php
2. Search for: 
define('WP_DEBUG', false);
3. Replace with: 
define('WP_DEBUG', true);
4. Add this line below:
define( 'WP_DEBUG_LOG', true );

Run a scan. The log (if any) will be saved to “/wp-content/debug.log”.

You can also adjust the configuration to use less server resource:
1.Basic Settings:
 -File Size > Scan only files smaller than : Set it to 100kb
 -Ignore file extensions: Add the following extensions:
po,pot,mo,css,png,jpg,gif,tiff,xml,json,woff,woff2,ttf,eot,yaml,svg,txt
 2. Advanced Users Settings:
 -Files and folders > Warn if executable files: Disable it.
3. Nerds Settings
 -File integrity checksum: Select “MD5”