All of the failing HifiBerry’s are using the same overlay - hifiberry-dac. I modified all of the soundcard overlays last week to allow dynamic loading and unloading, but in doing so I broke the hifiberry-dac version - sorry about that. I fixed it the next day, but @sam_nazarko was unlucky enough to get the bad one. You may be able to patch up your system by downloading this fixed version and overwriting your installed copy, otherwise I’m sure the next release will no longer have this problem.