Could be that the safety latch isn't fully releasing.
View from the top, fully latched.
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Roll down window, insert a push rod here. You can see this from above, I've verified this on my 73 Satellite. Push down.
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This is a 1/4" metal rod, A 3/8" might be better, 1/4" drive extension also works.
How it looks pushed down and fully released, notice the gap in the latch levers at the top.
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Hard to see this through the window gap at the top of the door. While pushing the rod down try opening the door.
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