There are some bugs with deinterlacing at the moment. Part of it is that it can get muddled about what the appropriate refresh rate is. It reads the file header and thinks “okay, 29.97fps”, switches to 29.97Hz output, then realises a few seconds later that it’s actually trying to output 59.94 progressive frames per second, tries to switch to 59.94Hz refresh rate, finds it has lots of frames saved up and tries to rush through them all at high speed, and then everything goes a bit off the rails… But if you can force it to output 59.94Hz right from the start then everything goes more smoothly.
I hope there will be some fixes for this in the future!
A video that is actually 1080p/29.97fps will be played at 59.94Hz without any visible difference - each frame is sent to the TV twice, but it looks the same to the viewer. Similarly 1080p/30 can be output as 1080p/60.
May I recommend my guide to the Whitelist…?