MS-Excel Sort with special chars: wrong result

I have some multi-language data, that means I use special chars like: á, À, ä, Ü, ß, etc.
Sorting cells containg this chars, shows this result (as an example):

that means: a < á < à < ä ... etc.
Fine! It is something like: a < b < c < d

The probelm rises as I add some other cells:

Because "a < á", when I sort all the values, I expect this sequence:

but surprise, the sort shows:

My first question is simply "why???"
But the real problem is that when I process these strings in VBA (macro), VBA evaluates (correctly!) "aX" < "ä", but in the sorted list: "ä" < "aX".

Any idea why the sort is not working correctly?
I already checked all the possible options in Excel Sort ...

Thx to @(Martin Brown) because he found the problem.
I copy here his comment:

"... The sort rule is converting accented characters to their unaccented form and then using length as a presort. It puts words with/without accents close to each other but in a funny way! The location of abc after sorting surprised me! – Martin Brown"