Gmx angle Fatal error

GROMACS version:2020
GROMACS modification: /No
Here post your question

Dear all,

I am trying to using GROMACS to do Principle Component Analysis by following this link:

However, when I reach gmx angle, I have this error:

Fatal error: Can not combine angles with trr dump gromacs

I have look through google and cannot find much information of that error, can someone explain how do I solve this?