Private catalog icons often disappearing and sometime later reappearing issue

The setup is as follows:

  • Rancher 2.1.3 server.
  • gitlab-based private repositories on an internal gitlab server; these are accessible using API token, and installing catalog apps from these private repositories works fine.
  • gitlab-based internal gitlab pages setup which automatically receives the catalog icons for the private catalog. These pages are internally accessible without authentication.
  • Firefox, Chrome, and Chromium web browsers.

How is Rancher and the Rancher UI using these icons and what kind of caching appears on potentially multiple levels? I’m asking because our catalog icons tend to disappear from time to time (more often than we like) to be replaced by the stock “book” icon. After some hours or days they often reappear, but it’s totally unclear to us what actually is happening.

This does not happen with public catalogs, though.

Can someone please explain the mechanics involved in Rancher catalog app icons, especially for private catalogs?