[HELP] Reducing frame rate 60fps ->30fps

[tomek398]

Windows 10
rev 2018.11.11.1

I need to reduce frame rate of my video clip from 60fps to 30fps without changing the duration of the clip. It comes from my mobile phone. I used Filtering->Speed Change->Scale Output Frame Rate. I set it to 30fps. 

When I play the output clip with VLC player audio is played normally however first half of the video is speeded up 2 times while the second half is just a still image (last frame of the first part). 

Any advice? What I'm doing wrong?

Thanks. Tom