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AD8302 overheating

I've been using two AD8302 modules for a project where S-parameters are measured. There are multiple functions, each with different codes and commands, supplying frequency sweeps from 0 to 4GHz at 0dB. Since the AD8302 is connected to directional couplers and not directly to the frequency generator, it receives around -20dB. The outputs were displayed fine, however, after a few days of using this code, the result started to just show -31dB as the magnitude ratio and the AD8302 IC itself was hot to the touch. The AD8302s are connected to an analog to digital converter (MCP3008) using the connection shown below.

Is it possible that a power surge occurred which burnt the AD8302s? Did the usage of frequencies upto 4GHz spoil the chip. Or is the fault entirely on the signal generating side? I am scared to connect any other AD8302s to the schematic shown as I fear it will just heat up as well.