Q: Do you know what is causing this amaryllis stem to bend?
A: It’s a fungal disease called red blotch or red fire, Stagonospora curtissi.
It originates from a diseased bulb but affected leaves or flower stems can shed fungal spores as well.
Treatment with a fungicide is difficult. The best cure is to discard the plant.
If this is your only amaryllis, and you like experiments, you could wait and see what happens.