video playback suddenly speeds up

[Pippi dataflow]

Hi there... I've just started using the SMPlayer (portable) on my windows 8.1 system and am very impressed with the quality of the image, the ease of use and it's customisability of keyboard shortcuts BUT..... I've been playing several mkv x265 video files and I encounter the same problem with all of them.... which is that sometimes, always at a scene change/edit the video playback speeds up to Benny Hill speed while the audio playback remains normal...???

I'm baffled... I've tried hard to find anything via google on this but can't find one single mention.... Anyone here has any idea what's going on and more importantly knows how to fix this...? The player is just not usable like this....

[Pippi Dataflow]

... To be more precise, it really seems only to be the x265 mkv format.

.... and when it happens I can rectify it, bring it back to normal speed by going back 10 sec (press left arrow) and then 10 seconds forward (right arrow).
This effectively takes me just passed the scene change point that seems to trigger the Benny Hill mode..... However, that's obviously not a solution that will work. If darling Acer is sitting on my lap I can do this (although NOT cool to be taken out of the story just to pay attention to some technicallities...) but when I watch something via little Acer-babe on the tv it's highly annoying to have to get up every couple of minutes.... (it's not at every scene change, just every now and then...)