I have definitely noticed this several times, in passing. Never huge enough amounts for me to go and make a comment, but I have also made special note when it happened that it was unrelated to starbase construction. I don't know how often this is happening, but I definitely had been noticing it around once per game (often when I went to look at resources for market prices there would suddenly be a downward DROP, inexplicably). Sorry, also no saved games (at university and definitely cannot risk having entrenchment installed and TEMPTING ME at all hours of the day!
If someone could confirm this with a saved game that would be great!
