Solved

What else he needs to b LVL 20

I just checked this by running the calculation which generates the overall values on this driver, and it says he is level 20...

It isn't hidden attributes, but it may be attributes which have since been hidden (actually, removed) in some cases, or some error in the calculation which has since been fixed. As this driver was created a year ago, it's hard to know what happened. That should be well after additional attributes from the old iGP were removed, which only leaves the explanation of some error updating his overall level.

Looks like something I'll need to repair manually, since he can't be trained any more. I'll scan the whole database for instances of this and try repair it today.

Haha, well I've just updated the overall level of all drivers. This should stop the exploit of getting a driver who is lower level than they should be then training them to find they are 2-3 levels higher.

As you can also see now Brijesh, your driver is level 20 as he should be.