The cast is no secret -- he fell in his sons' treehouse after getting startled by a Raccoon. The fuller-than-average story is he was collecting a tool he'd left in the treehouse's loft and moved a piece of plywood it was under . . . only to find it wasn't alone. Two steps back and he wasn't in the loft anymore. Bumped his head on the way down and landed on his wrist. This all the day before their last trip out west.
As for why spur of the moment things are consuming time in R&D . . . I think you misunderstand their process . . . or lack there of. Part of what they do and why we love the organic feel of the show is the "what if" portion, that is quickly played out and if it leads to a success or further ideas then it's pursued with gusto. If not, it becomes the every day work that gets time as they can muster.
As far as priorities (aka "Time better spent") they've got a great store now and good service . . . and the core IP of that store is being given away at no cost with no reuse restriction.
No other hobby shop would do that. That's because they're not a hobby shop. They're an entertaining education program, that gets funded by our patronage at the store. Semantics, some would argue, but the difference plays out in their priorities.
What drives the R&D isn't new products for us to buy (it does consume some of their attention, but it's a secondary priority), instead what's needed for the next episodes. The next episodes includes build videos and the accompanying plans -- we all love those -- but they've got a continuous flow of new models in the pipeline. The Shindin is one, although it's been in the pipe longer than average, but it's only one of many models under development.
Frustration aside (I get it. I want one too!) just like not releasing the airframes too early because an inconsistent build gets blamed on them, If they release their release schedule -- "update on progress" -- they get blamed for not giving their audience something free "On Time". Who likes to get blamed for missing a self-imposed deadline?
Relax. It will happen, when it happens, it will be sooner today than it was yesterday, and you'll be thrilled with it when it comes