It's also possible some just understood the question incorrectly or confused it with something else, not just "misclicked".
Without knowing how often this happens in other votings it's hard to tell if this is unusual.
There are a couple of explanations being floated. First of all there where two votes, not just one, and if you wanted to vote 'correctly' against A13 you had to vote NO on the first vote and YES on the second (or vice versa to support A13), The people who voted 'wrong' voted either NO to both or YES to both.
Secondly apparently the order of voting was changed at the last minute (there where a whole bunch of things being voted on that day) so people who had written down what they where going to vote on each issue (NO,NO,YES,NO,YES,YES,NO etc.) and missed that the order had changed would end up voting wrong. Ie. they knew they wanted to vote YES on issue 27, but issue 27 was actually the 28th item voted for that day. At least two MEPs in Sweden are using this excuse.
But basically a bunch of MEPs just didn't think it was that important to pay attention to the details, phoned it in, and screwed up badly.
Indeed. Epicenter.works published a table[1] to make it easier for people unfamiliar with the voting system to follow along. It uses the same template that the MEPs use, except with the "Vote" section filled in from the perspective of someone against Art. 11/13. This might make it easier to understand why this mistake could happen but it seems clear enough that, if you're actually paying attention, you could avoid mistakes on such an important issue.
[1] https://epicenter.works/sites/default/files/copyright_dsm_fi... (PDF)
I think the other issue is that for you and me and everybody here this is a super important issue, but for many of the MEPs it's just confusing regulation nr. 843 they have to vote on this year.
it's a complete joke, it goes so fast the interpreters can't keep up and people end up making constant mistakes
I think it was the other way around actually. They first voted on whether to allow an last batch of amendments, which would have allowed separate voting on article 11 and 13 (and this vote failed by 5 votes). Then only after that they voted on the real deal.
But you would never say this about an engineering system. If you had to make a series of poorly-marked binary choices in a certain order to correctly deploy a bugfix, and someone got that wrong, the postmortem would be about what a terrible UI that is and how it has to be changed to improve system reliability. An operator making an easy-to-make mistake would never be considered "at fault".
That's how we treat things that really matter for websites. Voting in parliament is a lot more important than that. I'd rather see a real postmortem and plan for improvement, not blaming the users.
Unfortunately this is not uncommon. Tools like Jira are sometimes configured with a maze of steps and jumps around the UI (buttons, fields, dropdowns, popovers in various orders) to get a ticket into the correct state.
The only number I could find where between 2014-2015 [1], but in that year the average was 6.7 registered 'mistakes' pr. MEP. So it seems to happen quite often, I guess it only rarely has this big consequences.
[1] https://www.europaportalen.se/2016/02/svenskt-rostvelande-st...