I've also noticed a sharp change in position since october. Was usualy placed at around 1800-2300 position and now im constaantly at 3000-3300 which has been resultin in a decline of around 25-30% sales. I've been in microstock since 2017 and I've always been very interested in sales metrics, trends etc and I always try to analyze whats making my sales change. Sometimes its one image that was popular that suddenly stops selling other times is the seasonality (for example its normal that in the last few weeks of december alot of non seasonal stuff stops selling). And im pretty sure that this is an algorytmn change because the only thing im noticing is an overall reduction of 25-30% in sales with no explanation.