Tooltips in custom visuals are appearing at the top left corner of the browser window in Power BI Online (screen position 0,0). This bug began around April 20, 2020.
I thought this might be a bug in my custom visual or a bug caused by conflicting libraries so I tried to test using a newly created, basic visual. This bug occurs in the update counter visual that is created by default in a new visual which is attached with minor changes to show the tooltip on mouse down.
This bug appears when a field is added to a category and disappears when the visual is updated either through a selection in a different visual in the report or by changing options in the formatting pane or adding a measure. The bug reappears if the field is removed and a field is added again. In reports with multiple data roles, the issue reappears when all fields are removed from the visuals and fields are added back in again.