I think light bends as it approaches the perimeter of the universe.The closer light gets to the edge of the universe, the more the mass from the rest of the universe is behind it. Near the edge of the universe, practically the entire mass of the universe is behind it, bending the light away from the edge and back towards the middle...
My theory of everything:
Eventually, things that appear to be very far away (the "oldest thing ever observed") may actually be bent light from closer things.
As light approaches the edge of the universe it should slow down, being pulled by the total mass of the universe behind it. Eventually that light will curve and turn back towards the middle. When that happens, the light will begin to accelerate again until it passes the center and begins slowing again as it hurtles to the opposite edge of the universe.
Each cycle should drain a little bit of energy, causing each cycle to be slightly slower than the previous one until the light particle finally stops in the center of the mass of the universe.
-PJ
Your light yo-yo theory won’t quite work because light is massless, but apparently they are also finding that it is massless for certain qualities but has mass for others, which once again is super weird.