IIRC Safari's default settings keep deleting your saved login, which is pretty unhelpful. I think if you change some privacy/tracking settings it should be able to remember it again - perhaps turn off some combination of the settings in the privacy section. Or just use Chrome or Firefox which tend to work better anyway.
Thank you, I'll try changing some settings and report back here if this helped me. But what other problems could I be facing if I continue utilising Safari for C3? Currently it has been my default browser for almost everything, so it'd be my preference to keep using it. But if there's any known issues I could stumble upon I'd like to be prepared and maybe switch to another Web browser purely for C3.