We're seeing the same issue and we are using a 6.7 uH conical inductors from Piconics. We see the same sort of thing. The current draw shoots up and the amp dies. It still passes a signal through it but there is no amplification.
We designed the Eval board for HMC788A by ourselves, but only got 8dB gain at 8GHz while should be 12+dB at datasheet. What is the concern for the PCB design? Can let me know the detail design information of the PCB structure?