Marcus Lausch tried your configuration and it works perfect for him. So far, there are two people who has a working unit. I start to think your firmware is probably not working as expected as I remembered you had issues to build one that I never had.
He also tried other configurations like through QD drive or external and it works for him. I'm not certain he tries the ultra-fast mode though.
Here is the link on his website : https://www.marcuslausch.de/2019/02/05/ ... mz-sd2cmt/