I work in a similar field to Passon and fully understand having difficulties on the manufacturing side. If like you say he is having problems with the main shaft it is much more difficult than just having a CNC machine popping out parts. Judging from the Passon website, he has not been manufacturing main shafts for 4 speeds, just reconditioning used ones. It is a steep learning curve to get these parts made properly. You'll have general machining, broaches for splines, heat treating, potentially specific tooling to machine the speedo gear and grinding to all get right. This one part has probably a couple hundred features which if any one is out of tolerance can potentially cause problems. And as someone who designs these parts it's also a game of having loose enough specs that the machining costs are kept under control while still getting a usable part. It can take many batches and years of tweaks to get things sorted. While the first transmission built and 500th will no doubt "work", there will be development over that time that will improve some aspect of it. It may not be noticeable and it might be a feature you only appreciate if you rebuild it yourself but no doubt in my mind there will be slight improvements. A much more complicated part that we started manufacturing back in 2009 (the design alone took me around a year) has undergone 24 revisions since then.
I have no ties to Passon but just thought some of you might appreciate a little insight. As much as I wanted a 5 speed it looked like he was having issues from the get go, so I opted for the Hemi OD kit and I'm currently building that transmission myself.
My advice is to keep your car running in some manner until you have all the parts in your hand to upgrade.
Good luck y'all!
Dave