Cannot create Maven 3.3.9 Executable while adding task into a plan

Scenario:

• Bamboo 5.9.7
• CentOS 6
• Maven 3.3.9 correctly configured
  In my local instance, I extracted the .tar.gz into /home/fkraemer/atlassian/apache-maven-3.3.9 and, after adding its bin directory into the $PATH environment variable, running mvn in Terminal worked as expected.
• When Bamboo starts, it detects Maven 3.3.9 automatically and adds it as Server Capability. Delete this capability.

Reproducing the problem:

1. Create a plan
2. Add a Maven 3 Task
3. The "Executable" dropdown will be empty of course. Click the "Add new executable" link.
4. Give the executable a label and ensure that the path is correct.
5. Click the "Add" button, and nothing will happen (the popup window will not close and the executable will not be created)
6. This is written in the logs:

   2015-12-30 16:18:06,044 INFO [http-bio-8085-exec-17] [AccessLogFilter] fkraemer POST http://localhost:8085/ajax/addSharedBuilderCapability.action 78082kb
   2015-12-30 16:18:06,106 WARN [http-bio-8085-exec-17] [TextProviderHelper] The first TextProvider in the ValueStack (com.atlassian.bamboo.configuration.agent.AddSharedLocalBuilderCapability) could not locate the message resource with key 'Please enter the Maven home value as your path. e.g. C:/dev/tools/maven-3.0.1'
   2015-12-30 16:18:06,106 WARN [http-bio-8085-exec-17] [TextProviderHelper] The default value expression 'Please enter the Maven home value as your path. e.g. C:/dev/tools/maven-3.0.1' was evaluated and did not match a property.  The literal value 'Please enter the Maven home value as your path. e.g. C:/dev/tools/maven-3.0.1' will be used.
   

Workaround:
Add Maven 3 at Bamboo Administration > Overview > Server Capabilities, and when adding a Maven 3 task into a plan the Executable dropdown will list it.