UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.30 Safari/537.36

Steps to reproduce the problem:
Repro here:

1. https://codepen.io/anon/pen/NppYrQ
2. https://flems.io/#0=N4IgZglgNgpgziAXAbVAOwIYFsZJAOgAsAXLKEAGhAGMB7NYmBvEAXwvW10QICsEqdBk2J4AbhgBOAAgCqcGDIC804AB000rdOoBXSZJGJV7DdulRaGACbGwutNWIR6ACgjWAlKrPnth4n1NLHxDAEddeGJXdU0-eJxiQlpbaTUQAHEAUQAVdIpfePN9KGN0kmIABzhEAHpawywAWkM4YiaMSogiRVoAa11Oyvw6LFrOiFrdBUk4WsQPfMKirWsMYgxjYA9jD1M4la0AdwgkgGFDaxEIDCga6WJJSIKDv1ZPZZX8JKZXe0dnG5WrooMRvLFDkV5IoRvpDAxpCpgaDPkV3st9ss4BgxDA7A4nC40K5waitAEgtIQuFIm0YmS-Ilkql0gAFWR5SgM4qSUppEAVap1BowZqtdoTHqSfqDSrDUbjLpTGZzBbWJavFZrDbGaGSWEGEQvSHHU6EC4wK4MG53YyPZ4M9GvVgaF1oDQSGR6gBitEkWERPle9AgaFO+IBRJJqj1+EsNlcAEZPPtzGIIDAjhHCW5SZr-DBApJgq50mA-Vh8tJkNztFhSyAoBgAEYwKBxlttqvpb0QWbEaSYHDpTzGk319Khyq6Yj4Kcz5DEACelRgSkYAA9iABdZCVJvUGDJKBXSRKXv9wdcbdViEm8whtDT4jGEInJIAQWIjwbEigkSrf4c2JP9InBWM9ENBh8EgfsADkuEDUCYHeMd7y0ZDdRmA14VnWC2gQ4d83iVDay0CdG07dsm1bKBuxAAAZDA2ivYcQFHMiqQbedZx4vcDyPWgT0UJQmJYocYBvSgg3Q7RH2fV98HfQgvx-dJkMAglARA24wJjbDINwjsCMQlRkNI4jDkwuQDLhERjOIQiYE4iz7wo5sZ2Ieh8A8796EXFc1zgXRmywU4pIoVR6GoKAIGoPosJhbFcXYfkAGUcWc9i0L8bcPmdV0NA0EIsFoBxomsWg9BwaDmxSJdIp9Ct8soEAFFgYCEB4AAWbrEAABjYDgQAkvARjgAQaHoRhmB4NhtyoWK0D6LrUBGrg8DCpJJGgAABNAYC3VqSjwQUanqBxKj6ABzEZaDGLbCB2qBdoAJnwfqPpaah8ETWpHue-B+Fa5dVzwOBqB2ypRFYbdWCAA

Open the dev tools and click "Save"

What is the expected behavior?
No requests to be canceled

What went wrong?
Probably about 80% of the above requests cancel in the first and about 10% in the second, if I had to estimate.

Did this work before? No 

Does this work in other browsers? N/A

Chrome version: 71.0.3578.30  Channel: n/a
OS Version: OS X 10.13.6
Flash Version: 

This was initially reported in https://github.com/MithrilJS/mithril.js/issues/1697