Steal the Aux button and plug it into the start/stop port on the card. When you pop the red cover back on, it’s identical.
Have you ever opened the ST 16? It’s not that hard. Of the three components, the ST is the easiest to open and service the switches, fans, and antennas. The two halves need a little force to separate after all the screws are out. Be careful not to pull the fan wires or battery connection apart. They are what’s part of holding the back half from separating.
The battery connector will pass through the gap in the rear half by removing the rubber grommet. The fan connectors need to be disconnected from the main board. The nut holding the switch should never be cranked on by a wrench. The little red cover will pop off when you pull the collar off the switch threads after unscrewing.
Since the aux will never do anything, it’s a spare part that gets you repaired in these situations. You could opt for a warranty repair as well and go through the RA request. That’s a lengthy process and equals no work or fun with your Typhoon for weeks.
You can also order the button switch and go that route which still would be a self repair. That’s what I did with my OBS switch when it popped apart. The first generation of that switch was a skinny pole and now it’s a flat spade. Even though their website said warranty repair only on that switch, I was able to purchase one on the phone with a Yuneec tech. So consider a call or chat with them and go over your options.