Detecting a box in bottom-right corner of image and cropping image to it

[forsberg72]

I have hundreds of images like this: https://ibb.co/pLthkX6

All the images have a rectangle around the whole drawing, and all have also that rectangle in bottom right corner. That rectangle contains smaller rectangles which contain text. I marked the rectangle with red arrow. How could I possibly crop images so that I only get that rectangle containing the important texts which I could possibly extract with Tesseract or similar?

Images vary in size and they can be landscape or portrait. I'm familiar with scripting/programming (e.g. Perl, Bash, etc.) and basic usage of IM tools, but I don't know advanced use of IM.