Here are some pictures of the PCBs in the Xiegu G90 transceiver.
The Main unit.
PA RF Board
Reverse voltage protection detail
NTC (Negative Temperature Coefficient resistor) problem
There is a serious gap between the NTC which compensate the bias for the temperature increase and the PA RF transistor case. This is one potential cause for premature failure in the final stage especially in TX intensive modes like FT8.
The solution is to gently bent the pins of the NTC to make physicall contact between them and apply a small blob of thermal silicone GLUE, not usual paste.
This will prevent a future gap due to vibrations or shocks and will increase the mutual temperature transfer thus an adequate bias voltage.