Hello Uli,
My understanding is as follows: When we use the command ‘apt install [package]’, it installs the requested package, but because it also tries to upgrade faulty packages, it gives the error ‘E: Sub-process /usr/bin/dpkg returned an error code (1)’ for those faulty packages. For example, when I use the command ‘sudo apt install nano’, it installs the ‘nano’ application correctly, but it gives the ‘E: Sub-process /usr/bin/dpkg returned an error code (1)’ error for the faulty packages. I would like this issue to be resolved. Was your question answered?