The Day gain/loss column in portfolio view is being calculated as the change in price from the previous day times the number of shares held on the current day, instead of by comparing the two market values directly.
This results in showing a huge erroneous loss when a fund pays out a dividend (lowering the price) and the shares held then increase due to dividend reinvestment.
Maybe someone else can confirm this is a known issue as it can needlessly lead to folks jumping out of windows!