When I play my colony at speed 3, i get ~113 fps after loading a specific save. This value is rather stable.
However, once I click on priorities and close it again, the fps permanently drops to ~103 fps. This can only be repaired be reloading a saved game.
To a lesser extend this is also true for the consumables tab (and maybe others).
This error was also reported by another guy (He assumes this is related to FastTrack, which i think is not).
Load the attached save file, unpause and let it run at speed 3 for ~10 seconds and observe fps.
Then reload the save file, click the priorities tab and close it, then unpause the game and observe fps as before.
See the difference in fps.
There is also an error in the player.log, which may or may not be related:
[11:29:33.018]  [WARNING] Insufficient keys to cover root plan menu Max of 14 keys supported but TUNING.BUILDINGS.PLANORDER has 15
I think this error occured the moment I opened the priorities tab.