Bugzilla

I also meant to note: if release is broken and Nightly is fine (as seems to be the case), there are two possible explanations:
(1) there's something that changed between the two versions that fixed the issue.
...OR:
(2) there's something different between the two user profiles, that happens to be related to the issue.

(Firefox release and Nightly each use their own distinct user profile). (This could be an about:config setting, or something in Firefox preferences, or a cookie, or an add-on, or some other sort of arbitrarily-strange accidentally-broken state.)

So if Nightly is fixed, it's not necessarily because it's a bug that's been fixed in Nightly; it could just be because Nightly got you a fresh user profile.

Again, don't want to discourage you from using Nightly, but if you happen to decide you prefer the official Firefox release again (instead of Nightly), then you might be able to avoid this issue if you start with a fresh profile; see https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles for notes on that.  (This would help in a world where the issue turned out to be category (2) rather than category (1).)

I also meant to note: if release is broken and Nightly is fine (as seems to be the case), there are two possible explanations:
(1) there's something that changed between the two versions that fixed the issue.
...OR:
(2) there's something different between the two user profiles, that happens to be related to the issue.

(Firefox release and Nightly each use their own distinct user profile.  The differing thing in (2) could be an about:config setting, or something in Firefox preferences, or a cookie, or an add-on, or some other sort of arbitrarily-strange accidentally-broken state.)

So if Nightly is fixed, it's not necessarily because it's a bug that's been fixed in Nightly; it could just be because Nightly got you a fresh user profile.

Again, don't want to discourage you from using Nightly, but if you happen to decide you prefer the official Firefox release again (instead of Nightly), then you might be able to avoid this issue if you start with a fresh profile; see https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles for notes on that.  (This would help in a world where the issue turned out to be category (2) rather than category (1).)