MongoDB returning field as null

I am currently working on an application connected to a MongoDB instance. I am having trouble where the 'id' field of my object is not being returned to me within the application but is being returned as null.

The schema has an 'entity' as defined below:

{
        "entity_id": String,
        "parent": String,
        "relevance": boolean
}

I'm querying the collection using the Java Sync Driver (4.4.1) like so:

try {
    Entity testDoc = collection.find(eq("entity_id", entity_id)).first(); 
    if (testDoc != null) {
        //add entity to a list
    }
} catch (Exception e) {
    LOGGER.log(Level.SEVERE, "Failed to get Entity", e);
}

For some reason this will give me every field in the object when I query EXCEPT the entity_id. I keep getting this returned as:

entity_id= null

Two things stick out to me. The first being that every other field is a String (originally the Id was a UUID object but I simplified while troubleshooting) and they still return if it's other fields. The second being that there is a whitespace before this null value as if it's being formatted. Other null values return as field=null instead of field= null

I was looking to see if there is some security setting preventing things from being labeled as *_id or *id from being returned but I have found no such instance.

Edit: Here is the Entity Pojo for clarity

public class Entity {

@BsonProperty(value = "entity_id")
private String entityID;
@BsonProperty(value = "parent")
private String parent;
@Deprecated
@BsonProperty(value = "relevance")
private boolean relevance;

public Entity() {}

public Entity(String entityID, String parent, Boolean relevance) {
    this.entityID = entityID;
    this.parent = parent;
    this.relevance = relevance;
}

public String getEntityID() {
    return entityID;
}

public void setEntityID(String entityID) {
    this.entityID = entityID;
}

public String getParent() {
    return parent;
}

public void setParent(String parent) {
    this.parent = parent;
}

public boolean isRelevant() {
    return relevance;
}

public void relevance(boolean relevance) {
    this.relevance = relevance;
}

}