How to specify index of specific elements in every sublist of nested list?

If a sub-list contains 'b' or 'd' that element must be in the first index [0]:

x = [
['a', [['b', 'c', [['e', 'd']]]]],
['a', [['b', [['e', 'd']], 'c']]],
[[['b', 'c', [['e', 'd']]]], 'a'],
['a', [[[['d', 'e']], 'c', 'b']]],
['a', [['b', [['d', 'e']], 'c']]]

def limitation(nested):
    for index, subelement in enumerate(nested):
        if isinstance(subelement, list):
            if not limitation(subelement):
                return False
            if subelement in ['d', 'b'] and not index:
                return False
    return True

for element in x:
    if limitation(element):
        print(element)  # ['a', [['b', [['d', 'e']], 'c']]]