Of course you’re right I don’t know for sure, I’m only guessing but if you’re interested I think that both the serial numbers on the right side are correct.
One of the serial numbers is 8782686 and it’s on both notes. Obviously one note has to be wrong they both can’t have the same serial number. So if we look at the bottom note there’s no doubt that the left serial number was the one having problems it even missed one number. So if the left side is wrong then the right side must be the correct number which is 8782686. Now if we look at the top note, if 8782686 is the correct number for the bottom note it can’t be for the top note too, that leaves the right side being the correct serial number again.
I think these two notes were only 200 apart from each other in the run and the printer started to make mistakes on the left side. On the top note only the first 6 was a mismatch and on the bottom note the first 6 and the 2 were mismatched and of course it has one missing number.
But like you said it’s only speculation, for all I know all four serial numbers are wrong.