Arch x64 Linux 4.9.8-1-ARCH
Short description of error
Blender Frame Rate is set to 29.97 fps.
Adding a Movie file of 1080i to Blender 2.78a and previous would add a movie and audio strip of the same (correct) correct length.
Adding the same file to Blender 2.78b and higher has the audio strip the correct length and the movie strip twice as long.
Here is the video stream information from ffprobe:
Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 59.94 tbr, 90k tbn, 59.94 tbc
If I change Blender's Frame Rate to 59.94, then the strip is the correct length. It's like blender is now reading the tbr/tbc value instead of the fps of the video.
I certainly don't claim to be an expert on video encodings, and I am probably saying this wrong. But the behavior is definitely different.
I've attached a small clip to experiment with.
Edit: The original upload did not exhibit the problem. Please use the file bad_clip_2.mts in my comment below.