O Video Downloadhelper / Firefox falha NS_ERROR_FAILURE

Question

O auxiliar de download de vídeo falha na minha máquina:

• clicar na seta de download em preto não faz nada
• clicar nas três bolas coloridas e escolher um formato também não produz, mas produz a seguinte saída do console:

console.error: downloadhelper: Message: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsILocalFile.create]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js :: exports.getDownloadDirectory :: line 8" data: no] Stack: exports.getDownloadDirectory@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:29797 Action<.getDownloadDirectory@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:2958 Action<.getDefaultTargetFile@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:1291 Action<.getTargetFilePath@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:1561 DownloadAction<.getDownloadTargetFilePath@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:16465 t@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:7323 e@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:7614 DownloadAction<.start/<@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:7737 a@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:5255 Action<.checkConverter@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:5772 DownloadAction<.start@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:7702 exports.perform@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/actions.js:8:28208 Hit<.action@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/hits.js:8:3202 exports.action@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/hits.js:8:5090 ToggleMainPanel/<.onMessage@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/main.js:218:5 HandlePanel/vdhPanel<.onMessage@resource://gre/modules/commonjs/toolkit/loader.js -> resource://b9db16a4-6edc-47ec-a1f4-b86292ed211d/lib/panels.js:133:7 emitOnObject@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:112:9 emit@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:89:38 emitOnObject@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:112:9 emit@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:89:38 emitOnObject@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:123:45 emit@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:89:38 postMessage@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/content/sandbox.js:347:7 emitOnObject@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:112:9 emit@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/event/core.js:89:38 onContentEvent/<@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/content/sandbox.js:397:5 delay/<@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/lang/functional/concurrent.js:38:20 notify@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/commonjs/sdk/timers.js:40:9

Versões de software:

• Debian Stretch
• Firefox 52.2.0
• Video Downloadhelper 6.3.1

Ele costumava funcionar bem e funciona bem em outra máquina usando o Debian Jessie com as mesmas versões do Firefox e Video Downloadhelper, mas não posso dizer com certeza que o problema data da atualização para o Stretch.

Não sei o que fazer com essa mensagem de erro. Isso deve ser considerado um problema do Firefox ou do Video Downloadhelper?