We have had to use a different solution. It looks like this function is not only causing UI issues but also performance ones. textWidth = textSizingElement.offsetWidth; Is a very cumbersome function when there is more than 1 autocomplete on a page. We have had to bypass this _getTextWidth function completely by returning a set value. looks this this whole function needs work.
Fix absolutely required, as the recent update has affected most of our customer facing systems. With no real interim solution this is a showstopper for us.