In a high capacity tray (2000 count) the plastic fingers are not located on the sides they are in the back. If the paper tray is reading the wrong size (i.e. reading legal when there's actually letter in there) - and adjusting guides and trying to fix it on the web interface won't work, the next option is to shut off the automatic sensor.
Once you shut off the auto sensor you can then pull the printer up online and change the tray size under paper menu.
To turn off the auto sensor, you turn off the device and hold down on the checkmark and right arrow buttons while rebooting and then you let go after the clock appears, and in the menu is a “Size Sensing” option that lets you turn it off and on.
When it is changed to off - you can select the correct paper size within the web interface so if you truly do want legal paper adjust guides but then select it online.