Occasionally when using Anki, a black bar will appear in the center of the screen that remains even after the application is closed. To remove the bar, I have to open task manager and manually end the task. See the attached photo:
Can you show us which add-ons do you use?
Try Display Issues - Anki Manual for a few weeks and see if the bar disappears
By the location of the black bar, could you try reinstalling heatmap?
Just tested and reinstalling shouldn’t restart your streak nor break, but be advised that it could
If problems persist after updating to the latest Anki version, you could try the different video drivers in the preferences screen to see if they help.