Publish showing docs that aren't qualifying the condition

I’m puzzled, all my pub/sub work fine so far but just this one is showing a weird behavior. I publish between two apps, hence the remote handle in front:

// Publish all groups
Meteor.publish('groups', function (kitUser) {
    'use strict';
    console.log('Publishing ' + Groups.find({ cousins: kitUser }).count() + ' groups docs');
    if (kitUser === null) {
        return this.ready();
    console.log('Kituser for Groups publish: ' + kitUser);
    return Groups.find({ cousins: kitUser });

This code gives me the following output on the server console:

Publishing 56 groups docs
Kituser for Groups publish: M102951

Which is exactly the right behavior, 56 groups docs are fulfilling the condition (in MongoDB terminal):

db.groups.find({ cousins: 'M102951'}).count()

But on the client app 58 documents are showing up (there are 58 currently in total in this collection):

As you can see, the cousins array in this doc doesn’t have the number M102951 in there. So it shouldn’t be published at all (and according to the count it isn’t) yet it shows up on the client.

Can someone tell me what’s wrong here and how I can solve this? Thanks in advance!