Thanks for the new details, Yoscoob. With no shadows, and with no GI/AO, something in the model must be the problem. Again, not having the scene here, makes it hard to tell. Perhaps check with the support! I assume frame 98 is not rendered always from the same CPU? But if so: Exclude each of the three, one by one, if you think it is the Team Render.
If objects do not move, only appear and disappear (do I go this right from the “on and then off screen”?), then some ideas should be considered/tested.
Bake the scene for each object appearance and render those, separately, edit the on and off like a movie later.
If the object do not move, bake only the area where they produce a shadow, and switch the texture when the objects appear accordingly.
If backing might not idea, camera mapping might. To get the shadow for the object, use the Compositing-Tag, and render from the animated camera at one frame. Copy the camera for that frame without animation, and use it as Projection Camera. (I have no idea about your scene, so this might—might not work that nice)
Normally shadow maps are not the way to go. If GI is used, AO is already included. To add AO on top of that increase the contrast in some areas, but AO is most likely not natural, compared to AO. A proper color grading is the better way, form my point of view, and faster.
Cheers
Sassi