Hi whpeng,
It seems from your log files that the convergence in the response function calculation goes completely erratic.
One general aspect that should be corrected is to allow for the calculations to reach convergence by increasing the number of steps. In all cases it seems that the calculations never reach the desired convergence target.
Since you are dealing with a metallic phase, personally, I would use a physical electronic temperature (Fermi-Dirac).
If other issues will arise I would suggest this older post PAW+DFPT+GGA has unreasonable energy values - #5 by baguetl
Please let us know if it doesn’t work out.
Bogdan