Since the OMC output power is close to 60 mW when OMC alignment is good, I reduced PSL output power by rotating PSL HWP.
Now, PSL output  power is about 2.2 W while it was 2.8 W before rotating HWP.
Since signals used for LSC except for CARM is normalized by IMC trans power, it doesn't affect the lock of FPMI (though CARM gain was reduced slightly but robust enough).

I'm not sure single arm lock is stable now (I hope it is also fine though), so if single arm lock is unstable please increase the laser power or adjust the gain of CARM CMS.