Description:

When we load rocket.chat webinterface the page stucks loading with the three loading dots.
Same is for https://open.rocket.chat

Steps to reproduce:

1. Start Internet Explorer 11
2. Browse to Rocket.Chat instance
3. Error: Page is not loading

Expected behavior:

Page should load like with all other browsers.

Actual behavior:

Page stucks loading with the three loading dots (animated).
IE11 Developer Tools Console shows a "Script1002:Syntaxerror"

Server Setup Information:

• Version of Rocket.Chat Server: 0.74.3
• Operating System: Ubuntu (4.4.0-104-generic)
• Deployment Method: Snap
• Number of Running Instances: 1
• DB Replicaset Oplog: Enabled
• NodeJS Version: v8.11.3

IE11 Information:

Version 11.2848.14393.0
Updateversion 11.0.115 (KB4489873)

Additional context

We tested with and without proxy, but problem exists with both.
We tested with and without reverseproxy, but problem exists with both.
We tested with and without GPOs / hardened security settings, but problem exists with both
We tested with and without ie11 compatibility view, but problem exists with both

Relevant logs:

IE Logs
SCRIPT1002: Syntaxfehler d1eef865fbf5b68bd6eb0f292fa51263c005b1ba.js (5,1702140)