XWPFDocument.removeBodyElement(int pos) throws IndexOutOfBoundsException whatever the value of the element index.

I think that this is caused by two XWPFDocument class code errors:

1 - In removeBodyElement(int pos), the statement:

bodyElements.remove(pos);

should be placed AFTER the statements:

Integer tablePos = getTablePos(pos); 

and

Integer paraPos = getParagraphPos(pos);

instead of before, otherwise the element is not there in the bodyElements List to be used to locate it in the paragraphs or tables Lists.

2 - In getParagraphPos(int pos) and getTablePos(int pos), the for loop should be:
for(int i = startPos; i >= 0; i--) {
....
}