The engine maker also aims to define a long-term solution by the middle of this summer
It's obviously not a fix if they still don't know how to fix it..
They know how to fix it with some help, concession from the customers.
The concession is adding more weight. So without the weight concession, I can't imagine what the fix might be.
The basic F135 engine design for the F-35 came from the F119 engine for the F-22 fighter. Both engines have about the same diameter, the F135 is 17 inches longer than the F119, mainly to accommodate one more LPT stage than the F119 has. The dry weight of the F135 is 150 pounds more than the F119, but with the aerodynamic changes to the fan and additional LPT stage, it produces 8,000 pounds of additional thrust in afterburner than does the F119.
However, that additional thrust is really needed to power the overweight F-35 aircraft. Adding engine weight to stiffen the engine backbone to stop flexing diminishes engine thrust to weigh ratio. Thrust to weight ratio can usually be improved upon by increasing turbine temperatures, but the turbines are already running at max or too hot which decreases turbine component life. So you see the probable dilemma.
