Issue Comments no longer displaying for users of Edge 17/42 after upgrade from 13.0.3 to 13.3.1

After upgrading to version 13.3.1 users that are using edge 17 are no longer able to view issue comments. They instead get the “Something went wrong while fetching comments. Please try again.” error message. The problem affects both our local installation and also GitLab.com. We were able to replicate this on GitLab.com by viewing issues on a private repository.

However, when following a link to a specific comment (e.g. “…/issues/2390#note_23846”) the comments are displayed without any problems. There are no errors in the logs, but it does seem that discussion.json is redirecting to the sing_in page. This is from the developers console in Edge:

We have an on-premises installation of GitLab and our host shows no errors in the logs, we can also replicate this issue when viewing issues in a private repository on GitLab.com

Our host seems to show discussion.json redirecting to the sing_in page. This is from the developers console in Edge:

Request URL: https://.../ediscovery/support/-/issues/2390/discussions.json
Request Method: GET
Status Code: 302 /
location: https://.../users/sign_in

And this is from '/var/log/gitlab/gitlab-rails/production.log'

Started GET "/ediscovery/support/-/issues/2390/discussions.json" for n.n.n.n at 2020-08-28 20:19:03 +0100
Processing by Projects::IssuesController#discussions as JSON
Parameters: {"namespace_id"=>"ediscovery", "project_id"=>"support", "id"=>"2390"}
Redirected to https://.../users/sign_in
Filter chain halted as :project rendered or redirected

For a page that loads correctly discussions.json return a 200 response, with this in the logs:

Started GET "/ediscovery/support/-/issues/2390/discussions.json" for n.n.n.n at 2020-08-28 20:39:53 +0100
Processing by Projects::IssuesController#discussions as JSON
Parameters: {"namespace_id"=>"ediscovery", "project_id"=>"support", "id"=>"2390"}
Completed 200 OK in 430ms (Views: 3.7ms | ActiveRecord: 98.9ms | Elasticsearch: 0.0ms | Allocations: 95837)

As far as i can tell, all requests for that issue page, except for the request to discussions.json have a cookie in the request headers, but in Edge 17, there's no cookie:

Accept: */*
Accept-Encoding: gzip, deflate, br
Accept-Language: en-GB, en-US; q=0.7, en; q=0.3
Cache-Control: no-cache
DNT: 1
Host: ...
Referer: https://.../ediscovery/support/-/issues/2390
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36 Edge/17.17134

Microsoft Edge 42.17134.1098.0
Microsoft EdgeHTML 17.17134