Filters Add Noise and Bad TV not working

Hi,

I installed the Motion 5 a few days ago and just started following the lessons of the Apple Pro Training Manual. Right at the beginning I am instructed to apply the Bad TV filter to a short piece of video (first and only layer and effect), but the filter does not work. To be precise, when activated, the video turns black or only runs 1 frame every 2 seconds or so.

I thought it would be because of the system requirements (I am using a MacBook Pro 2011, 4GB RAM), however, after rebooting the program a couple of times, the filter started working perfectly, for about an hour or so. Then the project got stuck to never work again, no matter how many times I closed and opened the program.

In the Library, when selected the filters "Bad TV" filter or "Add Noise", their preview is also blank (empty black square actually), which makes me think that there is something wrong with them.

Any ideas on what the problem might be, please?