I have also reproduced this issue and our users in production are severely affected. We received reports that multiple downloads were not working and comparing versions, I was running version 64 and they were running 65. As a test, I was able to download multiple files (14) with version 64. Then I upgraded to version 65 and immediately am able to reproduce the problem reported by our users. When I attempted to download 14 files again, there was inconsistent behavior. The first time, one file was downloaded. Second time, three files were downloaded. Third time, one file was downloaded.

I can reproduce the issue using a separate web application. On version 64, clicking "Download all" on the lower right of this script: http://jsfiddle.net/diegolamonica/ssk8z9pa/ brings up a prompt to allow multiple downloads. Once allowing multiple downloads, it will download 3 files: "file1.csv", "file2.txt", and "file3.js". Continuing to click the "Download all" will repeatably download copies of those 3 files.

Upon updating Chrome to version 65.0.3325.162 through the browser and relaunching it, clicking the same "Download all" button only downloads one file: "file1.csv." Repeated presses continue to only download that single file.

I am facing the same issue:
In my application, there are links to generate files with some relevant content and get them downloaded. While clicking on links for multiple files from same site, there used to be separate tabs opening for each link and were automatically closed once download is ready to start. However, In version 65 this behavior is broken and tries to open the subsequent links on the first tab opened overriding previous request. So one has to wait for previous download to finish before requesting a new one. By the time it gets fixed, is there any work around for parallel downloading?

dtrainor@, qinmin@, this looks to be an M65 regression preventing the download of large files - can you PTAL?

Able to reproduce #2, adding Hotlist-Enterprise

looks like a dup of 825100