We are seeing this with CE 0.38.0 / Pro 1.18.0 - The problem is visible for each browser we tried.
With fixed columns, vertical and horizontal scrolling renders the table well.
But when the context menu is used to to remove a row. Vertical (more visible as one scrolls to the bottom of the table) and horizontal scrolling cause the rendering to show the fixed column cells misaligned with the non fixed column cells.
The problem depends on the row heights being different for different rows - which occurs with the dummy data here due to text wrapping within the cells.
Here is a basic config fiddle showing the problem: https://jsfiddle.net/dehays/jadqc2pp/52/