Hi, sorry if this is the wrong area for posting this, this is my first time, I've been led to General discussion and don't know how to post in the "render" area, which seems to be more appropriate.
I have been using kdenlive for some time now, just to edit home videos, which it does nicely.
However, occasionally one of the clips in the rendered video freezes, for several seconds, before the video continues.
The clips come from my panasonic camcorder, these details are from mediainfo:

General
ID : 1 (0x1)
Complete name : /media/pete/dualntfs/aroundAust2016/00572.MTS
Format : BDAV
Format/Info : Blu-ray Video
File size : 17.1 MiB
Duration : 16s 313ms
Overall bit rate mode : Variable
Overall bit rate : 8 779 Kbps
Maximum Overall bit rate : 18.0 Mbps

Video
ID : 4113 (0x1011)
Menu ID : 1 (0x1)
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.0
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Format settings, GOP : M=3, N=12
Codec ID : 27
Duration : 16s 240ms
Bit rate mode : Variable
Bit rate : 8 037 Kbps
Maximum bit rate : 16.8 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 25.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Interlaced
Scan order : Top Field First
Bits/(Pixel*Frame) : 0.155
Stream size : 15.6 MiB (91%)

Audio
ID : 4352 (0x1100)
Menu ID : 1 (0x1)
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : 129
Duration : 16s 352ms
Bit rate mode : Constant
Bit rate : 384 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Delay relative to video : -80ms
Stream size : 766 KiB (4%)

Kdenlive reports that the video is 50fps, although mediainfo says 25fps. I use the HD 1080p 50fps to render, because of this.
I've tried the HD 1080p 25fps, no difference. I've tried both variable bit rate and CBR, no change.
When I discard the clip from the project, my movie is fine, but I'm wondering if there is a better solution.
Thanks very much

Your input material is interlaced. That divides 25 frames you see to 50 halffields per seconds. This is recognized as 50 frames by kdenlive. You should choose a 1080p25 profile for your 1080i25 material and ignore the dialog when importing files.

For the hanging clip I have two possible reasons: Does it have an effect or a transition applied? Some effects need progressive input and usually the interlaced input is converted automatically. Sometimes, if using the speed effect, the clip freezes. This can be worked around by adjusting the speed effects percent value. If it hangs by 50% it may perfectly work with 51 or 49.

Thank you for the information about the profile, I will choose the 1080p 25 profile in future.
The hanging clip has no transitions or effects, though, and in fact the same problem occurs when I render the clip on the timeline, by itself.