Gmx angle Fatal error

[btam125]

GROMACS version:2020
GROMACS modification: /No
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Dear all,

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

http://manual.gromacs.org/documentation/2019.4/reference-manual/analysis/dihedral-pca.html

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?

Best,

Ben