PREVIEW_RENDERING_FAILED - intermittent error

[JamesDean5655]

Have seen this posted a couple of times with no resolution.  Working on a large scale site, where the Embed API has been working well for months has in the last week started popping up with the error PREVIEW_RENDERING_FAILED, which fails to even show an error message, instead we get a completly blank screen.

The files are loaded from an API and converted to a bytearray returned via a promise, which  has not changed in any way, and the files sometimes load and then sometimes we recieve a blank screen and the error above. The files are not larged, max is currently around 2MB and the only way i can consistently show the error is if i 3G throttle the connection, just seems to time out even with small files.

The error seems to be thrown in ViewSDKInterfaceApp.js on line 54, which shows:

    previewFile(fileInfo, previewConfig) {
        this._logExternal("Starting process to preview file.", fileInfo.metaData, previewConfig);
        return this._embedModeHandlerService
            .initialiseAction(fileInfo, previewConfig, IFrameMessageTypes.PREVIEW, hostAppStartTime)
            .then(() => this._adobeViewer.getExposedAPIs({ previewConfig }));
    }

There are also some XHR requests going to https://dc-api.adobe.io/system/log which seem to have some additional information:

{
  "level": "error",
  "message": "Error in preview, file rendering timeout",
  "sessionId": "41188030-6b8f-47f9-9ab2-3b6dca66d104",
  "viewSDKAppVersion": "REDACTED",
  "tenantId": "REDACTED",
  "callingApp": "dc-view-sdk",
  "externalUserId": "REDACTED",,
  "clientId": "REDACTED",
  "client_timestamp": "2023-08-22T19:45:58.200Z",
  "context": "AppStore"
}

And

{
  "level": "error",
  "message": "File preview blocked as preview failed to load REDACTED",
  "sessionId": "REDACTED",
  "viewSDKAppVersion": "3.2.4_3.2.0-bab76ff9",
  "tenantId": "REDACTED",
  "callingApp": "dc-view-sdk",
  "externalUserId": "REDACTED",
  "clientId": "REDACTED",
  "client_timestamp": "2023-08-22T19:45:58.253Z",
  "context": "App"
}

[help2447472086ah]

Was running into a similar issue.  For me it was that PDFs were being setup ahead of them actually being rendered on the page.  If a PDF wasn't rendered in under ~60sec then this error was being thrown and the PDF embed would stop working.  However, if the PDF (or PDFs if multiple were present) were rendered on the screen the error wasn't thrown.

Solution could be to wait to until the PDF is visible before initializing the PDF viewer or render it hidden in some way. (display: none)