firefox error “file not found” when opening new (container) tab -> just hit ctrl-r

Today I started getting this weird error

File not found

Firefox can’t find the file at jar:file:///usr/lib/firefox/browser/features/!/chrome/content/prerendered/en-US/activity-stream.html.

When opening a new multi-account container tab. Then, after typing in an address and hitting enter, sometimes the tab would just hang forever, not loading or even not

Turns out if you refresh the page by hitting “ctrl-r” at this point, the tab will then load correctly. (The tab may otherwise be unresponsive to e.g. shortcuts “ctrl-l” or “alt-d” to go to address bar)

Not sure what the issue is, but I’m glad the workaround is easy.

Firefox 62.0.3 (64-bit)
Ubuntu 18.04.1