Too large shift between relaxed and unrelaxed positions

Dear all
When i calculated the phonons of SiY,Si2Y,Si3Y5,Si4Y5,the code gave me a message that too large shift between relaxed and unrelaxed positions.The procedure of calculation:
1.Fully relaxed the structure with ISIF=3 ENCUT=600 EDIFF=1E-4 EDIFFG=1E-4,then static calculation.
2.fitfc -er=10 -ns=2 -ms=0.02 -dr=0.1
3.Rerelaxed structure with ISIF=4 ENCUT=1.3*ENMAX,the other parameters are same with 1
4.Static calculation of super cell
How to avoid that or where is wrong ?

 Thanks

I responded to this question in another post. But the short answer is that when " too large shift between relaxed and unrelaxed positions" happens, it’s usually because the vasp run somehow crashed and the resulting str_relax.out is corrupted. Look for problems in vol_/p/str_relax.out and then work your way back in the OUTCAR* OSZICAR* etc. of the corresponding run.