Steps to reproduce: 1. Go to https://www.lullabot.com/articles/git-best-practices-workflow-guidelines 2. Right click on the title of the article and select "inspect element" 3. Wait until the markup and the rules are shown 4. Hard refresh (Ctrl + F5 on windows, Shift + Cmd + r on OSX) a few time Expected results: I always see the rules of the title on the rule view Actual results: Once in a while, the rule view gets empty, and the following message is logged in the browser console : TypeError: can't access dead object | devtools/server/actors/tab.js:1647:1 I couldn't reproduce with a simpler markup, so maybe there's a race issue with stylesheet load.

I get it 100% of the time with https://bugzilla.mozilla.org/buglist.cgi?bug_id=1405254%2C1404849%2C1404384%2C1405333%2C1408937%2C1408936%2C1408938%2C1405350%2C1405650%2C1405649%2C1405637%2C1405245%2C1406060%2C1408931%2C1403448%2C1405352%2C1405647%2C1405648%2C1405252%2C1403907%2C1408948%2C1404378%2C1403188%2C1403902%2C1408947%2C1401953%2C1404832%2C1408949%2C1408893%2C1404382%2C1406028%2C1405343%2C1404886%2C1408939%2C1403454%2C1404831%2C1404888%2C1403200%2C1408932%2C1404851%2C1408933%2C1405641%2C1408935%2C1401944%2C1403450%2C1406039%2C1401942%2C1403205%2C1408925%2C1401959%2C1405250%2C1408950%2C1405636%2C1404359%2C1406841%2C1406022%2C1408934%2C1404844%2C1404364%2C1404392%2C1408940%2C1401963%2C1404371%2C1401548%2C1405243%2C1404877%2C1408930%2C1408943%2C1404368%2C1405340%2C1408944%2C1405341%2C1404883%2C1408946%2C1408945%2C1403196%2C1408942%2C1404884%2C1408941%2C1406038%2C1404853&bug_id_type=anyexact&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&list_id=13960343 Currently bisecting

Couldn't reproduce so far, but that's a P1 for sure. Also reported here (in French): https://twitter.com/Wadj0s/status/951087313479749633 It looks like this is a Nightly 59 only issue. Let's make sure we get the fix in 59 too. [Tracking Requested - why for this release]: This sometimes prevents users from using the inspector, which is the most popular panel in DevTools.

Regression from Bug 1306892

Sending over to :jryans as discussed on IRC #devtools

This has the same root cause as the style editor version in bug 1429254. That bug has patches up for review, so most likely we'll have this fixed soon.

Fixed in 59 in the duplicate bug.