Possibly as suggested by Jonathan, wrong programming of the VFD. Its a very long manual, i know. But is unavoidable. Follow it step by step.

Check the phases on the motor! Wait for the VFD untill the led goes out after disconnecting before you touch anything!

The spindle can work hours without water without heating.

You don't need a pot right now. The button on the VFD rotates and you change the frequency.

Read the manual. the VFD stores last trips, you can go there and check what happened exactly, so no need to measure anything. During operation you can also monitor A, V and so on calling them on the display with a button.