It's very common for the PWM signal wire to fail, and it can fail intermittently - if plugging in the harness to a new fan it could have adjusted the wire to where it is now working again

If this new fan fails again, you should consider running a test piece of wire from DME x60004 pin 4 to the fan harness. If this works without fault run a new wire permanently. I've had to do this on many cars