User profile username change makes server unresponsive

Description:

When a user changes their username, the service will hang and/or crash hanging all clients connected to the service

Steps to reproduce:

1. Go to User>My Account:
2. Click on Profile
3. Change Username field
4. Click "Save Changes"

Expected behavior:

User name changed and saved to database

Actual behavior:

Clicking on save changes just sits and spins. Server no longer responds for the user changing their name, nor any other user connected. Seems to wait for a time out, approx 5 mins later, server starts responding again.

Server Setup Information:

• Version of Rocket.Chat Server: 0.65.2
• Operating System: Ubuntu 16.04
• Deployment Method: docker
• Number of Running Instances: 1
• DB Replicaset Oplog:
• NodeJS Version:
• MongoDB Version:

Additional context

Server was populated from a slack migration

Relevant logs:

Server log during name change:

API ➔ debug Success { statusCode: 200, body: { success: true } }
Meteor ➔ method getAvatarSuggestion -> userId: HXTT4zSKR6yFwcgNa , arguments:  {}
Meteor ➔ method checkUsernameAvailability -> userId: HXTT4zSKR6yFwcgNa , arguments:  { '0': 'zenjabba1' }
Meteor ➔ method saveUserProfile -> userId: HXTT4zSKR6yFwcgNa , arguments:  { '0': { username: 'zenjabba1' }, '1': {} }
Meteor ➔ method setUsername -> userId: HXTT4zSKR6yFwcgNa , arguments:  { '0': 'zenjabba1' }
API v1 Logger ➔ debug POST: /api/v1/subscriptions.read
Meteor ➔ method readMessages -> userId: HXTT4zSKR6yFwcgNa , arguments:  { '0': 'GENERAL' }
API ➔ debug Success { statusCode: 200, body: { success: true } }
API v1 Logger ➔ debug POST: /api/v1/subscriptions.read
Meteor ➔ method readMessages -> userId: HXTT4zSKR6yFwcgNa , arguments:  { '0': 'GENERAL' }
API ➔ debug Success { statusCode: 200, body: { success: true } }
API v1 Logger ➔ debug POST: /api/v1/subscriptions.read
Meteor ➔ method readMessages -> userId: HXTT4zSKR6yFwcgNa , arguments:  { '0': 'GENERAL' }
API ➔ debug Success { statusCode: 200, body: { success: true } }