It's possible to encounter this issue due to some settings that were changed when you re-installed the program. To fix this, make sure that when you create a new project, you choose for a high value resolution as well as for the Framerate. Also, you should check the Renders to be properly set to the value that you know that works for you. By default, this will be set to Auto-select. This might be the reason why you experience problems with the quality of your videos.