Jinxed-Schminxed ...

So, yeah... 

"unless - epic ninjas forbid - connecting the solenoids mess something up"

Guess what? 

I had messed up.

Almost burnt down the board since +48V pretty much forced all the gates open.

1) That mini-heartattack when you apply power, "all is well?" and suddenly smoke rises from the board
while the solenoids are going tick-tick-tick... 

I had pull-down resistors on the gates, but since the +48V and +5V didn't have a common ground the gates were essentially floating anyway. (Thanks for the help again, Majenko!) It didn't show up in earlier tests since I used +5V and ground from the board itself to test the circuit, but when the other supply was used it didn't work correctly. For some reason I assumed the high voltage power could be completely separated - and I realize how naive that was in retrospect. 

The fix was easy enough after actually finding the error, just a cable between GND & GND and Bob's your uncle...

...until I realized that I've somehow completely forgot to add pull-down resistors to pretty much all other MOSFET's on the board. *sigh*. So I'll have to fix that by soldering on resistors between gate and source even though that probably means putting components on the backside, but...

... my soldering iron broke down.

 
And now I play the waiting game with the Swedish postal service once again.
This build is cursed, I shit you not... 

But besides doing two lame n00bzor 2000-mistakes (which I didn't do when designing the circuits on breadboard, mind you) the machine can now flip balls.

And that's pretty dope. 

I also got two potentiometers in place to (in theory) help me dial in the opto's to only react to the IR-LED and not (as much from) the sun, for those rare Swedish summer days. 

2) Dialed In! ;) 
JJP are pushing out some high quality boards these days. STERN needs to up their game, imho... 

Footnote: 

I've been hunting a few bugs that are seemingly random - perhaps they too are caused by the floating pins. Would also be interesting to see if the +5V and +3.3V cables are required once all floating pins are properly grounded.