I’m able to reproduce this when I set media.autoplay.enabled.user-gestures-needed to false; if set to true (which is the default), unmuting does not pause the video.

(My) original report on Launchpad: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1820514

Any page under https://forums.tomshardware.com/ seems to trigger this, but I have yet to come across other sites that do. Pages can even be saved from the main Tom’s Hardware domain (https://www.tomshardware.com/) without issues.

A workaround discovered by Olivier Tilloy: clicking retry in the download manager completes the save.

Steps to reproduce:

1. Open https://forums.tomshardware.com/threads/what-is-the-actually-difference-between-udimm-and-dimm.1575984/
2. Right-click and select ’Save page as’. Point the dialog to your directory of choice.

Actual results:

There’s no copy of the page in the target directory. Going to about:downloads reveals that the download has failed, without further details.

Expected results:

For the directory to contain a downloaded copy of the page.

So I did a little more digging, and found that this actually first cropped up in Ubuntu 17.10.

I then ran mozregression (back on 18.04, my main desktop) and here’s what it found:

7:12.48 INFO: Last good revision: 64bab5cbb9b63808d04babfbcfba3175fd99f69d (2017-10-25)
7:12.48 INFO: First bad revision: aa958b29c149a67fce772f8473e9586e71fbdb46 (2017-10-26)
7:12.48 INFO: Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=64bab5cbb9b63808d04babfbcfba3175fd99f69d&tochange=aa958b29c149a67fce772f8473e9586e71fbdb46

After that ”There are no build artifacts on inbound for these changesets (they are probably too old).”

As this was my first time ever using mozregression, I have no idea how useful that was, but if there’s some way I can narrow this down further, I’d be happy to.

Adrian: Thanks for taking a look! I’m using Ubuntu 18.04, and that appears to be crucial here: I created a 16.04 VM, installed all in-release updates (including Firefox 63), and just as you, was unable to reproduce the issue. I then upgraded the VM to 18.04 and the bug immediately manifested again.

I first reported this against 62 in Launchpad: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1798103

Firefox was since updated to 63 in Ubuntu and the issue remains.

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:63.0) Gecko/20100101 Firefox/63.0

Steps to reproduce:

1. Open `about:config`, find `layout.css.devPixelsPerPx` and change the value from default (-1.0) to 1.2.
2. Open a view-source view with long lines: `view-source:https://www.youtube.com/user/10asti10`
3. hit Ctrl+f, search for rss
4. using the LMB, try selecting some text, then copy and paste it somewhere

Actual results:

After step 3, the highlighted text on the page is not ”rss”. The highlight doesn’t even adhere to letter widths (screenshot 1).

After step 4, the pasted text is not even close to what you’ve selected to copy.

Expected results:

For the search to hightlight an occurence of ”rss”, and for the pasted text to correspond to what I’ve selected from the view-source view.