wand.image.Image.export_pixel() width, height = right, top #413
total_pixels = (width - x) * (height - y)
Here is some code to test this claim and comments above each line are the errors I got:
with Image(width=50, height=50, background=Color("Green")) as image: x = 10 y = 10 width = 20 height = 10 #  86502 segmentation fault # export = image.export_pixels(x=x, y=y, width=width, height=height) # No issue here # export = image.export_pixels(x=x, y=y, width=width + x, height=height + y) """ python3(86545,0x7fff6b0635c0) malloc: Incorrect checksum for freed object 0x10401ea00: probably modified after being freed. Corrupt value: 0xff008000ff008000 python3(86545,0x7fff6b0635c0) malloc: *** set a breakpoint in malloc_error_break to debug  86545 abort python3 testing/wand_test.py """ # export = image.export_pixels(x=10, y=10, width=30, height=30) # export = image.export_pixels(x=5, y=5, width=20, height=50) """ I can't remember how I got this one Assertion failed: (image->cache != (Cache) NULL), function DestroyImagePixels, file MagickCore/cache.c, line 907.  86171 abort python3 testing/wand_test.py """
I'll have this resolved & create some additional unit tests to cover this. Probably in the next few hours.
No worries - just post a new Issue if you recreate it. Pretty sure the last one is an expected exception for authenticated pixels. The fix for the previous error should clean up the failed assertion.
Problem solved :)