Change the prop !
If this is another problem with the prop and at the moment it is a BIG IF then it should not be too hard to change the prop.
A number of manufacturers have props that are fitted to this engine who would jump at the chance of an order for 120 units plus a few spare.
Add the maintenance contract for prop overhaul and I am sure the package would be big enough to get the manufacture to get the certification done for next to zero cost.
The likelihood is that with the advances in blade technology the aircraft performance would also be increased.