I saw an explanation on another forum. With these coins the obverse, reverse and edge milling are all put on in a single striking, so the much hyped on the £2 coins "upside down edge" is not possible. So the only way this can happen is if a die has been incorrectly set up in the machine. The Royal Mint
wont acknowledge as an error, but I think it must be, and they seem to have fixed the problem as time has gone by. (Around 1 in 20 had this error in 2016, but around 1 in 800 for 2017. Not certain yet if it occurs at all on the 2018 and 2019 coins.)
The link in my post above goes into more detail on this and other errors (real, imagined and manufactured) on these coins.