Exception while browsing the tags in page creation wizard: The method transform(Object) of type new Transformer(){} must override a superclass method - AEM

Exception while browsing the tags in page creation: The method transform(Object) of type new Transformer(){} must override a superclass method - AEM 

We were getting the following exception while browsing the tags in page creation wizard - http://localhost:4502/mnt/overlay/cq/gui/content/coral/common/form/tagfield/picker.html?root=%2fetc%2ftags&selectionCount=multiple&_=1554223439347 500 (Server Error)

The below exception is displayed while trying to open the above mentioned URL

Compilation errors in /libs/cq/gui/components/coral/common/form/tagfield/datasources/children/children.java: Line 78, column 3367 : The method transform(Object) of type new Transformer(){} must override a superclass method
Cannot serve request to /mnt/overlay/cq/gui/content/coral/common/form/tagfield/picker.html in /libs/cq/gui/components/coral/common/form/tagfield/datasources/children/children.java

Exception:
org.apache.sling.scripting.java.impl.ServletWrapper$CompilerException: Compilation errors in /libs/cq/gui/components/coral/common/form/tagfield/datasources/children/children.java:
Line 78, column 3367 : The method transform(Object) of type new Transformer(){} must override a superclass method

Steps to resolve the issues:

Clear the compiled JSP cache:

The compiled jsp class files might have corrupted, follow the below steps to remove the existing classes and recompile the JSP's

Go to http://aem-host:port/system/console/slingjsp
Click Recompile all JSPs.

Unfortunately the specified issue was not resolved after clearing the cache.

Verify the Source VM and Target VM in Apache Sling Java Script Handler:

Ensure the the Source VM and Target VM values are specified with the version the AEM server is running or specify as auto to automatically consider the current VM version.

In our case the VM version was pointing to 1.5 but our current VM version is 1.8, the issue was resolved after changing the VM versions to auto.

This issue was observed in AEM 6.4 version after upgrading from AEM 6.2, the same VM version(1.5) was working in AEM 6.2 without any issue.

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