You've shown that the physical input works, with the hard wire. If the extender also provides a hard wire from the receiver, and that's what you're using, then no amount of software can help. You're getting a bad signal from the receiver.
Wireless is inherently unreliable. There are ways to help that, but never eliminate it. If you're less than 25 feet, just run an HDMI cord. If you're more than 25 feet, convert it to SDI, run a coax, and convert back to HDMI at the receiving end.
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If you only just thought of the technical stuff less than 24 hours before the show......well, now you know to start earlier!
We're using a pair of plywood horns that I made over the last few weeks, with a mic in the bottom of each one, to pick up our kids better. I bought the first set of materials about a month in advance, and even with procrastinating a lot, I still finished three out of the original two that I'd planned. (I didn't like how the second one turned out)