Is this a known bug?
with v1.19-pr3 in HTML5 autorotation prevents the onidle event from firing. This is not the case in Flash or with v1.18 in HTML5. This is true in every browser I've tried in Windows 7.
You can see for yourself in the following examples. Each starts with autorotation disabled and an idletime of 6 seconds. You will see that onidle fires and switches panos. Click the autorotate toggle button and you will see that onidle no longer fires but only in v1.19 HTML5.