Here's an odd one:
I changed the POV in a scene and moved a population of birds to a new area. I then edited individual instances of the birds to new positions and angles, saved the scene and rendered. In the new render the edited birds hadn't moved, either in the render or the preview, yet the preview before rendering showed them in the edited positions!
So I edited them again saved the scene (with the preview still showing the new positions), saved then rendered again. Same result: birds hadn't moved. Tried re-populating: same thing. Tried saving, exiting TG, rebooting, reloading : same result edits not remembered.
Finally tried "reset modified" in the populator even though no instances had been modified other than moving the whole population to a new point, and it worked. Birds now in edited positions. Is this a bug? Or what causes the instances to need resetting?