If I recall you did a basic type of install where the contactors operate the VFD inputs. Have him take the VFD wires going to the contator (P24 and Input one and have him connect those two to a switch and see if the VFD will run forward when he closes the switch (spindle needs to be in the stop position. Alternative is to switch the two VFD input wires 1 and 2 at the contactors (or at the VFD) and see if forward now runs with the spindle is in reverse. If it does it sounds like a contactor problem and he can use a different pole, I would also have him check the wire connections for the VFD low level inputs, give a light tug to the input wires at the VFD, and also have him reseat the connections at the contactors.
Contactors are poor conductors for low level signals, in particular if they were previously used for high voltage switching. In addition in humid hot environments they can corrode quicker. You can have him contact me if he needs to dig a bit deeper and that doesn't address the issue. VFD would not loose it programming, either works or it doesn't.