Random "502 Bad Gateway" on initial directory load, refresh works.

Hello,

Thanks for this great software. I'm sure this is user error, but I'm stumped. I'm running FileRun (docker-compose) behind HAproxy, and I'm getting random "502 Bad Gateway" on initial directory loads, but using the refresh button in the webui or hitting reload on the browser fixes it.

I can watch the 502's come in very quickly in the browser dev console. And they will all reliably load after a refresh. 1 or 2 images in a large directory may load on an initial load.

When I copy direct image URL from the web console, it will never fail to load, which makes me think this might not be proxy related.

When searching for this fault description, I found this exact match in another piece of software. Probably unrelated, but posting here in case it makes sense to someone. https://github.com/shipping-docker/vessel/issues/97

Any help appreciated!