Text added to Video layer not displaying correctly

Hi, new member here - 1st post.

When I add the Text filter to a video layer, it works fine. When I add text to a colour that that has had the opacity reduced to 0 (as per the tutorials on this site), my text is displayed as an jaggedy outline:


If I export, the jaggedy outline is retained. Any solutions anyone is aware of? I am new to Shotcut and it seems a powerful piece of software, so i am hoping i can resolve this! Thanks, Andy