Your front wheels aren't moving after changing the Unit Bearings or Hub assemblies.
You may have installed the wrong unit bearings. XJs changed the Unit Bearing designs and hat depth between early and late model XJs. If you install the wrong unit bearing, the brake rotors become bound once you torque everything down. Here are the correct part numbers for the Wheel bearing / Hub assembies by year:
Source: https://naxja.org/forum/showthread.php?p=243386895