OK, well my solution was just removing the guilty code, as it is not necessary for the page to run correctly.
But I posted the bug here:
https://bugs.chromium.org/p/chromium/issues/detail?id=1016235&can=2&q=save as pdf
I am sorry but this did not solve my problem. There are some items that simply refuse to disappear from history whatever I do, whichever guide I follow on the web.
I have a suspicion it has something to do with the online synchronisation of my data - I think they are stuck online, and even after clearing my cache, these entires get downloaded back from my Opera account.