I would like to find the coordinates of the divergence points of the double helix in a temperature change electrophoresis image of a gene, that is, the coordinates of the position of the mark in the attached image.

I collected sample images and tried to find the coordinates of the bending points using the Predict function and NetChain & NetTrain and NetChain & NetTrain, but the accuracy was too poor.
I tried using ImageCorners but the accuracy was still an issue. Is there no other way than to resort to tedious programming?

Predict function

NetChain & NetTrain

ImageCorners