Manual analyze still not working for generating video preview thumbnails

I have reported an issue where auto generate the video thumbnails a while ago here Video preview thumbnails are no longer being generated automatically . I’m posting on this thread since I now have another issue with generating the thumbnails.

If I remove a library (I’m upgrading it from SD to HD), in other words, deleting a library such as Friends which I recorded on TV originally and then deleting the thumbnails via ‘troubleshoting - clean bundles’ and then replacing the series with the new purchased blurays, the thumbnail genrates only one or two frames for each episode.

Does anyone have any idea on how to fix this?