JasperSoft Studio not recognizing self-defined function libraries

Question

I'm running into a problem with JaspersoftStudio. I had a working project with a library defining custom conversion functions. Lately my .jrxml views don't find my functions anymore.

When clicking on preview of file1.jrxml in folder [PROJ_ROOT]/set1, following error message is thrown:

"The method AUTO_CONVERT(String) is undefined for the type file1_1434540912649_515329"

AUTO_CONVERT is located in [PROJ_ROOT]/src/de/companyname/packagename/MyClass.java, all variables passed to it are of type String. Sample from MyClass.java:

package de.companyname.packagename;
..
@FunctionCategories({ de.companyname.packagename.MyClass.class })
public class MyClass {
..
@Function("AUTO_CONVERT")
@FunctionParameters({ @FunctionParameter("aString") })
    public static String AUTO_CONVERT(String aString) {
...

The jasperreports_messages.properties file is in [PROJ_ROOT]/src with content (also tried moving it to same dir as Myclass):

de.companyname.packagename.MyClass.name = MyClass
de.companyname.packagename.MyClass.description=Custom Functions
de.companyname.packagename.MyClass.AUTO_CONVERT.name = Auto Convert
de.companyname.packagename.MyClass.AUTO_CONVERT.description= Descr

jasperreports_extension.properties, also in [PROJ_ROOT]/src:

net.sf.jasperreports.extension.registry.factory.functions=net.sf.jasperreports.functions.FunctionsRegistryFactory
net.sf.jasperreports.extension.functions.test=test

Previously I managed to fix these kind of problems by modifying the build path settings and simply adding the project root ( which doesn't change anything now ). My functions don't appear in the expression editor.

JasperSoft also seems to have some kind of problem "acknowleding" my src folder. Instead of displaying a folder like src directory in the Project Explorer and de/companyname/packagename as subelement, it now displays src/de/companyname/packagename as one single element. My classes packagenames are marked red and expect src as a prefix (src.de.companyname.packagename instead of de.companyname.packagename)

I can trick JasperSoft into "acknowleding" the src folder by chosing New->SourceFolder in the project root, but this gets changed back by some JasperSoft magic after a while.

Moving to de/companyname/packagename and working without src fixes the packagename issues, but still my views don't recognize my custom classes.

My class path looks like this:

<?xml version="1.0" encoding="UTF-8"?> 
<classpath>
        <classpathentry kind="src" path=""/>
        <classpathentry exported="true" kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
        <classpathentry exported="true" kind="con" path="net.sf.jasperreports.JR_CONTAINER"/>
        <classpathentry exported="true" kind="con" path="com.jaspersoft.server.JRS_CONTAINER"/>
        <classpathentry kind="output" path="bin"/> 
</classpath>

Anyone have an idea what may be going wrong and how to fix this? I'm pretty sure it must be something with the project setup. Simply creating a new one didn't help either.

Strangely when I chose the FunctionsLibrary wizard and have JSoft create example methods + a sample report, the expected hello world function fails with a JRExpressionEvalException for the Hello World message. If relevant - sloppy example or my mistake?

Thanks

Update:

I fixed the strange src folder behaviour by doing this: .classpath:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
        <classpathentry kind="src" path="src"/>
        <classpathentry excluding="src/" kind="src" path=""/>
        <classpathentry exported="true" kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
        <classpathentry exported="true" kind="con" path="net.sf.jasperreports.JR_CONTAINER"/>
        <classpathentry exported="true" kind="con" path="com.jaspersoft.server.JRS_CONTAINER"/>
        <classpathentry kind="output" path="bin"/>
</classpath>