Code snippet for reproducing the issue with retrieving objects from ParseRelation from a Local Datastore.

gistfile1.java

public void BugReproduction_ParseRelation_getQuery_fromLocalDatastore() throws ParseException {
  // Let's create a simple Post ParseObject
  ParseObject post = new ParseObject("Post");
  post.put("author", "Aleksandar Ilic");
  post.put("text", "This is a post.");
  post.save(); // Post gets saved on the Cloud with objectId "Q46yLYlx7e"

  // And some comments
  ParseObject comment1 = new ParseObject("Comment");
  comment1.put("text", "This is 1st comment.");
  comment1.save();
  ParseObject comment2 = new ParseObject("Comment");
  comment2.put("text", "This is a 2nd comment.");
  comment2.save();
  
  // Now we are going to put the Comments in the Post
  ParseRelation commentsRelation = post.getRelation("comments");
  commentsRelation.add(comment1);
  commentsRelation.add(comment2);
  post.save(); // Updating the post in the cloud
  
  
  // After a while ...
  // ... we want to query the Post from the Cloud
  ParseQuery query = new ParseQuery("Post");
  query.whereEqualTo("objectId", "Q46yLYlx7e"); 
  ParseObject networkPost = query.getFirst(); // Success - Post from above fetched
  networkPost.pin("Post"); // Pinning the ParseObject for offline usage
  
  // And also the Comments
  List<ParseObject> networkComments = networkPost.getRelation("comments").getQuery().find(); // Success - 2 comments found
  ParseObject.pinAll("Comments", networkComments); // Pinning the comments for offline usage
  

  // After another while ...
  // ... device went offline and we want our Post
  ParseQuery localQuery = new ParseQuery("Post");
  localQuery.fromLocalDatastore();
  localQuery.whereEqualTo("objectId", "Q46yLYlx7e");
  ParseObject localPost = query.getFirst(); // Success - Post found in local datastore

  // And again also the Comments
  List<ParseObject> localComments = post.getRelation("comments").getQuery().fromLocalDatastore().find();
  
  /*
   * Expected result is that 'localComments' (fetched from Local Datastore) have 2 comments
   * as it was the case with 'networkComments' (fetched from the Cloud).
   *
   * Actual result is that 'localComments' has no comments. It's an empty list.
   */
   
   // Important
   // If a "Comment" class would have a pointer to a "Post" class everything would work fine.
   
   // Notes
   /*
    * (1) Code from the above is written with the purpose to reproduce the issue.
    *
    * (2) Pulling the database from the devie and viewing it with SQLiteManager
    * reveals that Comments are pinned and available in the database.
    *
    * (3) In my production app (not related to this code example) I'm experience
    * this issue after the app has been killed by the system or force closed by the user.
    * Basically, it works only until the app gets purged out of the memory. 
    */
}

We try to reproduce the issue using your code, but it seem that the code not work and need some modification

Why you used query nested of localQuery at this line? https://gist.github.com/AleksandarIlic/88881d4de3b187bb34c9#file-gistfile1-java-L40, we replace them and the code works perfectly

Can you please help us reproduce the issue so we can help solving it.