IE11 - SyntaxError: Invalid character at parseResponse in iron-request

[rbjarnason]

Description

After upgrading my rather large app to Polymer 2 I have iron-request sometime throws IE11 - SyntaxError: Invalid character at parseResponse

Expected outcome

Iron-request should not crash

Actual outcome

I managed to capture this screenshot of the problem with the full error coped to notepad - it is very difficult to debug in IE11, I seem to have to wait for 5-10 minutes after a crash until the dev tools start responding and showing me errors.

Live Demo

https://betrireykjavik.is/group/47 (if you click on add new idea or something that will trigger the login screen IE11 it will crash with this error)

Steps to reproduce

I have only been able to reproduce it in my app which is open source here: https://github.com/CitizensFoundation/your-priorities-app

Browsers Affected

• [ ] Chrome
• [ ] Firefox
• [ ] Safari 9
• [ ] Safari 8
• [ ] Safari 7
• [ ] Edge
• [X ] IE 11
• [ ] IE 10

[rbjarnason]

I caught this problem above with Break on all exceptions in IE11 but if I set it to break on only Unhandled Exceptions - I get "Failed to parse JSON from undefined" - which would not be a problem except that IE11 becomes unresponsive for at least 30 minutes (on a VirtualBox 4 CPU instance with 4gb ram) - I came back to it 4 hours later then it had this message:

[rbjarnason]

Actually this turned out not to be the issue that is causing IE11 crashes so I'm closing this.