@thomas303: E10S (which triggers this issue) was only enabled in FF 51 when using non-whitelisted plugins. So this might be the difference between previous versions. Where disabling all the plugins enabled E10S, and thus caused the issue.
@thomas303: E10S (which triggers this issue) was only enabled in FF 51 when using non-whitelisted plugins.
So this might be the difference between previous versions. Where disabling all the plugins enabled E10S, and thus caused the issue.