Just what is the impact of finding these errors, and how can it be corrected?
“...wouldn’t that mean that a manual recount would determine the actual winner since software counts wouldn’t have paper ballots?”
Not necessarily. The machine reads paper ballots which are fed into it, and then scans and stores an image as back up.
Assuming the paper ballots fed into the machine were valid, and were retained and unaltered - then yes - a physical recount would determine the actual winner.
Unfortunately, we can’t assume any of that:
The paper ballots could be invalid to begin with - recounting them would not make them any more valid.
Valid paper ballots could be altered prior to being read into the machine - recounting would not fix them - it would just repeat the error.
The physical ballots could be destroyed, altered or created AFTER being processed by the machine - in which case an accurate recount would no longer be possible.
Re-checking the validity of a physical mailed-in ballot may be impossible if the outer postmarked envelope, or voter signature and ID, had been separated, descarded - or never been secured in the first place.
The problem with unsolicited mail-in ballots is that they are based on an unverified registration list.
The problem with allowing mail-in ballots to be entered days after Election Day, is that it is easy to obtain the list of registrees who did NOT respond - and make up fake ballots for them.