I had this issue and confirmed that I couldn't copy files out of the 7z archive using normal compression. I tried a few things in combination (unfortunately) so I don't know which step solved it. First, I uninstalled my SE classic unlock license. Second, force-stopped the app then cleared cache. Afterwards I could extract the blank text file. I reinstalled the unlock and it still works. I'm using a Pixel 2 XL with Android 8.1
I had this issue and confirmed that I couldn't copy files out of the 7z archive using normal compression. I tried a few things in combination (unfortunately) so I don't know which step solved it. First, I uninstalled my SE classic unlock license. Second, force-stopped the app then cleared cache. Afterwards I could extract the blank text file. I reinstalled the unlock and it still works. I'm using a Pixel 2 XL with Android 8.1