When several clips are stacked it is sometimes difficult to select the right clip in the Program Monitor.
So select the clip on timeline and double click, this will open it in the Source Monitor. Then go to Effect Controls and highlight the word Motion. Now the ‘circle’ will appear.
Do you have the same issues with a non Matrox project?
I.m.o you dont need a Matrox with a 975. I have a 940 with 12 gig RAM and edit HDV like DV, dont even have to render Magic Bullet Looks for preview.
Using preview files makes encoding much faster but can cause quality loss, due to only one cycle of encoding.
Best is to use Max Render Quality, needs lots of RAM and takes a lot of time.
Very difficult to say.
If you know of someone who has an AVCHD camera try and get some footage to test.
There is some test footage out there, do a Google.
You can start here: https://www.kdenlive.org/forum/h264-avchd-raw-footage