It happens, especially with plastic in the fixture instead of aluminum. Heat causes slight warping. I usually try to gently move any pieces back in to shape by hand. Granted there's no guarantee against cracking or breaking. Only sure fire way to prevent that is to buy new parts or a new fixture.
Im so paranoid I'll bust the bulb forcing it in.. one end slides in as you would imagine..but the other end you have to slide the prongs through the top of the opening.. and that is where it gets stuck..
This model is discontinued.. so I don't think I can get a new one..
Here is what I ended up doing.. I took a pocket knife and gently shaved a little of the plastic to make the slots just a tiny bit bigger.. then I grabbed my set of precision screw drivers.. you know the tiny ones that come in the plastic case?
Lol anyway.. a little dab of silicone grease and pushing down the prongs with the screw driver get them in..
Now.. the next problem I have is my tank is just a tad too long to set the light fixture on top.. I had to order a set of tank brackets online.. I PRAY that they will work when they get here because hanging the light from the ceiling is not an option..
This entire tank set up has been a frigging McGyver episode from the filter to the lights.. my next adventure will be the C02 no doubt as I have never done that before either.. lol