Bigger projects during scanning present IDE error in notifications and present fake errors

Window > IDE Tools > Notifications

Priority / Message / Date Created / Category
Zz / unexpected Exception / 1 minutes ago / Error

After click on link for reporting of issue and click to be shown details
so there is only text: java.lang.NullPointerException

Additionally it is seen that "Background scanning of projects..." takes really enormous amount of time on project with hundred of classes that ends with such fake errors and notification above.

Some classes reports fake errors that it is not possible to fix by any of these ways:

• close project and open
• reload project
• clean and build
• scan for external changes
• modification of file
• creation new file in same folder and remove
• removal of Apache Netbeans cache (under option --cachedir)
• removal of caches/6.4.1 under gradle home

So only way what helps:
Opening step by step each such classes where such methods are implemented or to theirs return types of methods and so on and renaming such targeted classes that seems lead to an invocation of "Background scanning of projects..." on source file that leads to disappear such fake errors. Take to consideration also that some classes seems as they do not exist even in dialog for Type (CTRL+T).

So I guess that it should be revised a "Background scanning of projects...".