Check the rings
It also looks like maybe one of the rings is upside down. If you look at the one shown on the left you can see a notch in it at the top. You don't see a notch on the other one. Now I haven't seen one of these particular tractors in person, I would venture to say that the notch should be on a "key" tab, on the back of the lamp.
After going back and looking at the photos, you definitely have one of the rings on upside down. the ring on the left shows the notch at the top the one on the right shows it at the bottom.
As I said there should be a "key" boss on the rear of the lamp, this is to keep it from spinning in the mount. If that Key is not lined up in the notch, it loads all the pressure into that point rather than around the whole diameter.
I believe if you put a new lamp in it and make sure hte rings are located correctly you won't have any more issues.
__________________
Gary
1974 1650 50A "budscub" Was my fathers
1969 125 42"
1978 1450 44A dual hydraulics
1984 782 50C dual hydraulics, waiting for vanguard
Z-force Cub cadet Zero turn
Sears '66 Suburban 10 Sears '66 Suburban 12
2 Breaking plows, 2 disc's, front blade, rear blade, Sickle bar mower, 2 decks 3pt harrow
74 "Green 100 "John" 
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