Late in the game, the UFP had a proposal to set the minimum speed for Constructors higher than whatever the base is. My constructors I had designed had a speed of around 33, so I wasn't too worried about it. I forget which option passed, but the minimum speed was indeed raised.

Well, the law passes, and what do I find?

My constructors can move 33 spaces on their first turn. Then they are limited to 6 moves a turn. Their speed, when first built, is set to 33/6.

This seems to be a bug, to me. I tried redesigning the ship (to 37 Speed, they became 37/6 movement), and reloading the game.

Rather annoying to be playing on a huge map with 6 speed constructors. :/ For 4 game years, no less.