Inverter keeps giving me an over current error (1.5kW inverter error OC-r). However this is now making a cut that is 80% lighter than when I first received it. Do you know any way to fix this?

Make sure to check all of the connections from the VFD to the Spindle and make sure here isn't any short in the wires. That would be the first thing to look for. If that is not resolving the issue, check the programming parameters related to the current and torque setting to make sure that those are within the expected range.