What transmits when the pico is connected from a computer?

Which pins do you use to connect the cord to the Pico?

And are you using the most recent firmware?

Please can you try using just the most basic VGA output example (so nothing else):

var g = require('tv').setup({ type : "vga",
  video : A7, // Pin - SPI MOSI Pin for Video output (MUST BE SPI1)
  hsync : A6, // Pin - pin to use for video horizontal sync
  vsync : A5, // Pin - pin to use for video vertical sync
  width : 220,
  height : 480,
  repeat : 1, // amount of times to repeat each line
});

g.drawLine(0,0,100,100);

And see if you still get the same problems?