Intermittent 500/502 from CDN while origin returns 200 on mp3 requests

Hello,

We serve public mp3 files from a DigitalOcean Space (fra1) with CDN enabled. The files are consumed by a Unity WebGL app (Unity 2022.3.69f1) that preloads and plays many voice clips via UnityWebRequestMultimedia.GetAudioClip. We use Sentry to capture errors. Even before enabling origin logs, we saw intermittent 500/502 on some mp3 requests. After enabling Spaces origin logging, we observed that the origin replies 200 while the client sometimes receives 500/502 from the CDN.

Concrete origin log example:

[10/Jan/2026:14:23:47 +0000] - tx00000af6d21948dbd738e-00696260f3-1ae3d551-fra1c s3:GetObject /StreamingAssets/Voices/fr/Theory/Chapter4/Theory4_0_answer1_Explanation.mp3 "GET /StreamingAssets/Voices/fr/Theory/Chapter4/Theory4_0_answer1_Explanation.mp3 HTTP/1.1" 200 - 53184 - 6 6 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36" - - - ECDHE-RSA-AES128-GCM-SHA256 - fra1.digitaloceanspaces.com TLSv1.2 - -

At the same time, Sentry reported a 502 on that URL. This suggests the edge CDN returned 500/502 while the origin served 200. The issue is intermittent, appears during bursts of mp3 requests (audio preload in WebGL), and seems to hit random files.

Any idea or advice on why 500/502 is returned while origin is 200?

Thanks in advance.