I love the FM3, but the looseness of this USB connection has been bothering me from day one as well. I don't want to mount my FM3 to a pedalboard, so here's my homebrew solution to give me a bit more peace of mind that it will stay in place. It's not pretty, and really doesn't eliminate much of the "wobble", but having the support of the second USB connection definitely holds it into the socket more securely. And in the process I found at least some use for that extra USB-A connection. 
Simple steps:
I dug up a couple of charging cables with USB-A ends, some Loctite plastic glue and a few 3:1 heat shrink tubes. It was easy to saw the metal plug end off the USB connector which I'm using simply as a spacer between the other two cables. I glued the two USB-A connectors together first and plugged them into the FM3. I then put glue on the side of the center spacer, plugged in the USB-B connector and pressed those together for a few seconds until the glue set up. A little heat shrink tubing, and now I have a not so beautiful, but stronger connection. Rock-n-Roll!
Simple steps:
I dug up a couple of charging cables with USB-A ends, some Loctite plastic glue and a few 3:1 heat shrink tubes. It was easy to saw the metal plug end off the USB connector which I'm using simply as a spacer between the other two cables. I glued the two USB-A connectors together first and plugged them into the FM3. I then put glue on the side of the center spacer, plugged in the USB-B connector and pressed those together for a few seconds until the glue set up. A little heat shrink tubing, and now I have a not so beautiful, but stronger connection. Rock-n-Roll!
