A couple times now I have noticed that building 5 individuals Frigates/Destroyers cost less then building the 5x at once...
I.e. Time is 2 for an individual ship, or 11 to build the 5x.
I seem to recall in earlier builds it was the other way around. Building the 5x generally saved you a bit of time.

This isn't a bug, just a case of the UI being unintentionally misleading. The 5x actually does cost less than producing five ships individually. What's you're seeing is caused by the leftover production from the previous project being factored into the listed number of build turns, which usually reduces both by 1 turn. This results in the 1x looking like a better deal even though it isn't.

ahh... good to know! thanks :)