The DAWG file on the website should contain the original word list, and it did contain double letters.
Normally you can print its content with the "listdic" tool, which is part of the Eliot distribution on Windows (on other platforms you will have to build from source) or using the dictionary tools in the interface.Unfortunately, I gave it a try and it seems that the special letters are not displayed properly. It is probably also the reason why you don't have these letters when playing...
You should probably try with older versions of listdic from the Windows archives, in case it is a bug in the latest versions. Once you recover the original word list, you should be able to compress a new DAWG, which will hopefully work better (let me know if not).
Happy new year! :)