[clarkss12]

""Thanks for the Reply, this sounds to me like those channels are US based, is that correct? As I am based in Europe, the channels here are encoded in 1080i h264 at 25fps. So therefore there is a test clip in the Kodi samples WIKI linked here (Sample 1080i h264 at 25fps Video) and if you could test that, it would be great. It should playback if everything works well at 50fps and there should be no interlacing lines. 

Another question. Is it possible for Kodi to switch resolution if you set the box to be at 50Hz as a standard. I am just not sure if the box needs to be set to automatic (which would probably result in a standard 60Hz frequency) and as most content here is 25fps, setting the box at 50fps would not lead to much frequency switching apart from watching a movie at 24fps.

Hope that's not too complicated phrased what I have written in the second part of this post. Tricky to phrase it if english is not you native language "

I ran that video clip using Kodi, with the "HDMI self-adaptation" turned "off" your file play without any dropped frames BUT LOTS of skipped frames.......  With the "HDMI self-adaptation" set to "total mode", the Mecool KM6 switched to 25fps as shown from my TV stats (see photo), and played perfectly.

https://imgur.com/x624s7v
https://imgur.com/8LCHqWW
https://imgur.com/t9WXucl

Here is the "Mediainfo" information about your test clip, notice the information about framerate.
Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline
Format level                             : 4.1
Format settings, CABAC                   : No
Format settings, Reference frames        : 3 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 1 min 0 s
Bit rate mode                            : Constant
Bit rate                                 : 14.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 50.000 FPS
Original 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)                       : 0.135
Stream size                              : 100 MiB (98%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

I just tested my Mecool KM2 that does NOT have any frame rate switching, and the video clip played without any dropped or skipped frames.  My TV stats showed 60fps, so I am not sure what this video clip proves......