Interesting. That probably means that your code was right to begin with, but you had not re-executed the cell after you fixed the last bug in it. If you type new code in a function and then just call the function again, it runs the old code. You have to actually click “Shift-Enter” on the modified cell in order to get the new code “compiled” (well, “interpreted” really) into the runtime image. Or doing the classic:
Kernel -> Restart and Clear Output
Save
Cell -> Run All
will get things back in sync so that WYSIWYG. 