Combine slider and video in appdesigner

In appDesigner I am trying to use the changingSlider callback to move between frames in a video.

My code has a RunAnalysisButtonPushed function that processes a video and adds markers to frames, saving each frame in the property

app.outVid(:,:,:,nFrame)=processedVideoFrame;

within a while loop. This function also starts the video player on specific axis in the UI as

imshow(vidIn, 'Parent', app.VideoDisplayer);

where vidIn is the very first frame shown within said funtion.

A second function TimeSliderValueChanging aims at displaying the frame as the slider is moved by

video_updater(app,round(event.Value))

function video_updater(app,nFrame)
            imshow(app.out(:,:,:,nFrame), 'Parent',app.VideoDisplayer);
end

The code works as inteded althought the image displayed is as follows:

I don't understand why the colours are not displayed properly.

What I have tried and did NOT work:

• I have run the engine of this code in matlab (not in appdesigner) and the procedure of saving the modified frames with the method outVId(:,:,:,nFrame) shown above does not modify colors when played back in a for cycle with a figure and imshow, therefore I exclude that the method of saving the frames is at fault.
• I have displayed the frames within RunAnalysisButtonPushed as they were being calculated and WITHOUT saving them in app.outVid but within a temporary variable internal to the function RunAnalysisButtonPushed and colors are diplayed correctly

It seems to me that the problem lies within trying to store the frames in the app property app.outVid

What could be the cause of this? And how can I work around it?

Thank you