my needs were not very low but i went to a services house to green quick, went to work and my needs dropped back to what they were before i greened. I managed to finish 4 rounds at the bot factory and lure 1 afk sim onto the track (never freeload at the bot factory when there is a sim with lure around) and when i went home my needs were greened up to the point i had started at.
So next round im gonna green up fully, leave the house and go to another and then go to work from there. By my reckoning i should be fully green when i get to work, and fully green when i get back from work
EDIT - i just fully greened one of my sims at one house and sent her to another house. When she arrived she had lost all the green she had just worked on and arrived very red at the new house. I greened her up fully there, then sent her on to another house where she arrived with all her needs lost again.
It looks as thought the problem is that we are losing any green we have gained as soon as we leave the house, or to go to work. The lower your needs get the more difficult it will to be actually able to go to work given that you cant green there. This obviously needs urgent attention