• VSCode Version: 1.33.1
• OS Version: Windows 10

Steps to Reproduce:

1. In a CSS file where multiple RGBA square box can appear on the left of a rgba(1,1,1,1) or even a hex color like #ffffff.
2. Make a multicursor selection by pressing mouse left click + Shift + Alt
3. Have multiple color square box in the same line. (more make it easier to spot)
4. just try to move the cursor and farther they are in the line with color box, the cursor are following less the mouse.
   Gif to represent it :
   

I was taking fun to edit vscode css to get my own personalize editor theme as I discover the Custom CSS and JS loader extension. So I slowly edit the CSS file and I try to make animation through linear-gradient. Bad Idea as there is no transition between each animation, but when I try to make multicursor edit, I found out that the cursor wasn't spawing where I was clicking but a bit on the right of where I click so I test it out and found out those box break where my selection should end and my mouse is.

Does this issue occur when all extensions are disabled?: Yes