If the file has already been saved with Companion in one of the Shared folders (eg /Documents) on Android 11+, then this file cannot be overwritten with the APK afterwards because it is a different app.
You only saved the filename with a timestamp of the day, so this wouldn't be possible again until the next day, as that's when the filename changes.
The options are:
Delete the file with Companion beforehand or
Uses a timestamp with Mdyy_HH-mm-ss (in the filename).