Business Central throws validation error with "$" while using enumeration in Guided Rule Editor

Issue

• Let's say an enumeration is defined in a class in the following fashion. It has been archived in a Jar and the Jar is uploaded into Business Central's Artifact repository location , so that it is available in order to draft a rule in Guided Rule Editor.

public class EnumeratedFact {

     private EnumeratedFact.TestEnum enum;
     private String firstName;
     private String lastName;
...
     public enum TestEnum {
     ...

     }
...

Now, in order to use it to draft a rule through Guided Rule Editor while attempting to Import the enumeration in Config tab, the enumeration is displayed having the $ sign in the class name instead of . . Java uses $ internally for inner classes, hence Business Central should use . instead. Now, while writing the rule in form of a Add free form drl option, where the rule is written that uses the enumeration having the name like EnumeratedFact.TestEnum.XYZ .
As soon as the rule is saved and the Guided Rule Editor refreshes the rule , it converts the enumeration appearing in the form of having a $ sign in it's class name, like EnumeratedFact$TestEnum.XYZ. This causes a validation error for that rule in Business Central.

ERROR [org.drools.compiler.kie.builder.impl.AbstractKieModule] (pool-18-thread-3) Unable to build KieBaseModel:defaultKieBase
Unable to Analyse Expression 
...
[Error: unable to resolve method using strict-mode: org.drools.core.spi.KnowledgeHelper.EnumeratedFact$TestEnum()]
[Near : {... EnumeratedFact$TestEnum.XYZ ....}]

• What is the root cause of this issue and how to fix it?