That does indeed feels like a potential bug, though I've never seen that happen before. I'm actually somewhat confused by exactly how that happened. Does Ctrl-R do the same thing? If you need, you can disable aspect ratio lock by holding down shift while resizing.
This has already been fixed, but why would you enable deinterlacing on a webcam? Webcams are hardly ever interlaced.
Hmmmm, interesting. I'll try some other deinterlacing options. When the feature first came out I tried all of them and the retro one seemed to look the smoothest.I've seen this happen to another person and it only seemed to happen when they were using the field or retro deinterlacing filter.