Trjconv error

GROMACS version:2019
GROMACS modification: No
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Dear developers and users,
I have been trying to dump a few frames in a pdb file using the trjconv utility by supplying with an index file containing the atoms I want to use further post processing calculations however I have been encountering errors with the same.

Command line:
  gmx trjconv -f traj.xtc -o _pid.pdb -n index.ndx

Will write pdb: Protein data bank file
Reading file topol.tpr, VERSION 2019 (single precision)
Reading file topol.tpr, VERSION 2019 (single precision)
Note that major changes are planned in future for trjconv, to improve usability and utility.Select group for output
Group     0 (         System) has 131341 elements
Group     1 (        Protein) has 15056 elements
Group     2 (      Protein-H) has  7568 elements
Group     3 (        C-alpha) has   968 elements
Group     4 (       Backbone) has  2904 elements
Group     5 (      MainChain) has  3868 elements
Group     6 (   MainChain+Cb) has  4800 elements
Group     7 (    MainChain+H) has  4792 elements
Group     8 (      SideChain) has 10264 elements
Group     9 (    SideChain-H) has  3700 elements
Group    10 (    Prot-Masses) has 15056 elements
Group    11 (    non-Protein) has 116285 elements
Group    12 (          Other) has   456 elements
Group    13 (            FAD) has   336 elements
Group    14 (            UMP) has   120 elements
Group    15 (            SOD) has    20 elements
Group    16 (          Water) has 115809 elements
Group    17 (            SOL) has 115809 elements
Group    18 (      non-Water) has 15532 elements
Group    19 (            Ion) has    20 elements
Group    20 (            FAD) has   336 elements
Group    21 (            SOD) has    20 elements
Group    22 ( Water_and_ions) has 115829 elements
Group    23 (    Protein_UMP) has 15176 elements
Select a group: 23
Selected 23: 'Protein_UMP'
Reading frame       0 time 30000.000   
Precision of traj.xtc is 0.001 (nm)

Program:     gmx trjconv, version 2019
Source file: src/gromacs/gmxana/gmx_trjconv.cpp (line 1355)

Fatal error:
Index[14924] 15177 is larger than the number of atoms in the
trajectory file (15176). There is a mismatch in the contents
of your -f, -s and/or -n files.

Moreover, when supplied with a tpr file containing the same group of atoms which I generated using convert-tpr I encounter segemntation fault and the same thing works when supplied with the original tpr.

Moreover, I would want to ask is there any better way to dump frames in a pdb file without such hassle.

Anticipating your suggestions and answers.
Pallav Sengupta

Hi Pallav,
If you provide to gmx trjconv (with the option -s) the tpr you use to run the simulation and create the index file you will not encounter the problem (as you also wrote) .

Concerning convert-tpr, I think the functionality you use (I guess number 2) is not ** fully functional**.

Please let me know if I did not understand completly your issue