Troubleshooting the Meike MK-RC7

My Meike MC-RC7 radio camera/flash trigger encountered an issue over the weekend that I was fortunately able to resolve. I'm not sure how it got fixed but I'm sharing what I did in case in helps anyone else with the same issue.
My parents were in town and my mom wanted a simple family portrait. I setup the camera on the tripod and connected the MC-RC7 as we got ready for the shot. I did a couple of test shots and noticed that the trigger was strangely unresponsive, although it did fire a couple of times. I didn't have time to look into the issue and I was forced to resort to the camera's self-timer, which isn't as effective as using a remote and caused quite a few missed shots (like the one above).
Afterward, I inspected the MC-RC7 receiver (RX) and the transmitter (TX) and found that the batteries were leaking and part of the battery on the TX had rust. I removed the batteries, cleaned both of them, then inserted new batteries.
With the new batteries inserted, I would be able to get the camera to focus, but it couldn't trigger the shutter. I could see that the LED on both the TX and RX were changing (red then green when triggered) but somehow it wasn't causing the shutter to release.
I tried it several times to no avail. I then tried to press the RX trigger by itself, which did trigger the camera. Then I tried to move the TX unit close to the RX before triggering it, and to my surprise, it triggered the camera successfully. I moved it further and further away, successfully each time, until it seemed to work from normal distances.
Info on the shot above:
- Mix of ambient and flash.
- Ambient was from a patio door camera right and behind. Ambient was underexposed by 0.7 to 1 stop. Ambient was assisted by...
- an SB-800 was on TTL mode, on-camera, bouncing to a wall/ceiling camera left and above. It was also a CLS AWL commander for...
- a gridded SB-600, also on TTL mode, to add hair/rim light.
- D300 + Tamron 17-50 VC
- Also used Targus TG-P60T with Opteka TS-1 ballhead

I think out of several attempts the one I like the best we managed was this (and on this one the SB-600 didn't fire because I didn't notice it was on the wrong CLS channel):