I'm having issues, too. I use an OEM wired Xbox controller and have been a bit annoyed at it. So far I've used three different plugins:
1. UCCNC OEM plugin. I suspect that's the one you're using.
2. Xbox plugin #1 found on CNCZone in the UCCNC forum. This is a beta(ish) plugin that uses the analog joystick functions as a proportional control. http://www.cnczone.com/forums/uccnc-control-software/300622-new-xbox-jogging-plugin-volunteers-test.html
3. Xbox plugin #2, also found on CNCZone. This one I haven't got working yet as I think it's dependent on some .dll I don't have. It throws up when I enable it. http://www.cnczone.com/forums/uccnc-control-software/314206-plasma-thc-amp-xbox360-controller-plugin.html
The OEM plugin must be configured for the buttons/switches/joysticks to work. In the default state only the A/B/X/Y buttons are mapped to movement functions. Everything else is blank. Do yourself a favor and print out the list of button commands from the Documentation folder where UCCNC is installed and go through it while the plugin configuration window is open. Map the button function number to the button and save it.
My problem is that even though I mapped the buttons and joysticks, the joystick are still binary (on/off, not prportional). I may not have mapped the buttons correctly. I'm used to the Mach3 Xbox plugin and that was wonderful.
The plugin #1 (above) I've tried works (joysticks are proportional), but the left/right triggers are not editable on the configuration screen. They are permanently set to be 'high-speed' buttons that increase the jog rate from 50%-100% Nice if you've got an 8 foot router; not so nice if you've got a small mill.
What I want is for the triggers to be a safety button - must hold a trigger to enable any movement. Other folks responding to the thread where the plugin was posted requested the same thing, but the thread died early last year.
The other irritating thing is the step value. The right joystick left/right is set up to switch between .001/.01/1/.1 steps. Way too easy to nudge it and crash a tool when I'm sneaking up on something. Because the step value is only displayed on the jogging flyout I have no idea what the step value is. The 'vibrate' feature is supposed to alert you to the step value, but I'm not comfortable with it. I've changed the step values while jogging the Z-axis accidentally.
If you get any of the pluging working to your satisfaction, please report back and let me know what you did. I'm seriously missing the Mach3 Xbox features.
Also, if you or anyone else knows how to change the default step value I'd be eternally grateful. UCCNC defaulting to 0.01" and not 0.001" is aggravating but I can't find a setting in the configuration tabs.