Hi,
That's not really a bug, because the thumbnail is supposed to be smaller than the original picture (it's called thumbnail afterall ..)
Anyway, I know how to do it.
And not really many lines will have to be added to achieve that.
So to be sure , please do confirm that i did understand you correctly : you cant the thumbnail to be the same size, same aspect-ratio as the original video.
If you agree i can start this today, and deliver it less than 24hours working perfectly.
Of course you only pay upon job completion (I work in set-top box firmware department of STMicroelectronics, so what you want to achieve is a very common task for me ..)
Contact me back if interested.
Cheers