I am on Nightly which updates 2x daily without problems. If restart doesn't work maybe try a re-install. Filing a bug would be great so Firefox devs can work with you to find a root cause.
On Windows it should background update now as well.
Firefox member here – thanks a lot for reporting those bugs! Thanks to detailed reports Debugger could improve and glitches should become more and more a rarity.
Please report those via webcompat.com – Firefox's compat team will always follow up and learn more how to close the platform gap that causes the issues but also reach out to the devs.
DevTools member here. We have been working on performance over the past release – is there anything specific that you can point out as being slower for us to focus on?
DevTools member here: We have a more powerful target switching (hidden) in the toolbar but are also working to better expose JS context switching early next year.
Debugger's new threads panel also solves this partially when you pause in a thread.
Are your use cases extensions, workers or iframes?