First of all, it only occurs with non 100% transparent widgets where the color is picked by a HEX value, e.g. Simple Calendar Widget. I've attached 2 screenshots, the first shows the problem, the second shows how it should look like (made while swiping through the different homescreens).
Widgets from the top to the bottom with ascending transparency in 25% steps from 0% to 100%. You can see, no errors with 0% and 100% transparency but with 25%, 50% and 75% and there also only where left from the widget a white background is. The error takes (from left to right) as long as the background remains white, when the background changes from white to black, the error stops.