WordPress post slugs

I was happy to find out that when you activate permalinks in recent versions of WordPress it will automatically generate the post slugs to make the URL’s look nice.

I have one problem though. In Denmark we use this special character ‘?’ which should be converted to ‘aa’ not just a single ‘a’.

The thing is that it converts it to both ‘aa’ and ‘a’, the algorithm is inconsistent so to speak.

Example 1 (? is translated to two aa like it should be)
Example 2 (? is translated to just one a, should not be like that)

Can I somehow change how the automatic slugs are generated?