The HLS interstitial asset list was downloaded but could not be parsed: the body was malformed JSON or did not
contain a valid ASSETS array. An empty (no-fill) response is reported as a warning instead, not an error.
The HLS interstitial asset list could not be downloaded (network error or a non-2xx HTTP response).
An HLS interstitial asset failed during manifest or media playback.
Error codes for server-guided ad insertion (SGAI) / HLS interstitials.
These are carried in code of an AdError event whose top-level ErrorCode is MODULE_SGAI_ERROR, and can be used to identify the exact cause of the failure.