Failing to delete JMRI object state listener and mqttPubEvents class object instance

[jonasbjurel]

Describe the bug
Failing to delete JMRI object state listener (addPropertyChangeListener()) and mqttPubEvents class object instance.

1. JMRI method: removePropertyChangeListener() Seems not to work, check with a newer JMRI version
2. JMRI method: addPropertyChangeListener() Seems to create 2 callbacks per event, check with a newer JMRI version
3. Cannot delete mqttPubEvents class object as the JMRI callback generator has a reference to the object.

To Reproduce

Expected behavior

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Additional context