I remember back during the very first community event there was a bug where going through the portal took you to an entire different universe if your playthrough was not on the initial universe you start with. I lost my base and progress and I never found a way to get back to my universe so I just stopped playing. lol
Was this ever fixed or am I forever forced to just start a whole new save?
Honestly even if you didn't lose everything, starting fresh is the way to go after all these changes and updates. It's a pretty different experience with different quest lines and significantly different QoL mechanics. I started fresh and enjoyed my new save considerably more than my previous one (especially since you can play with friends).