**Summary** I am trying to generate a trajectory file for the last 500 ns from a 4 us one and resetting the time to be like a 0 ns to 500 ns trajectory: ``` gmx trjconv -f step7.xtc -o step7_mol.xtc -pbc mol -s step7.tpr -b 3500000 -t0 0 ``` **GROMACS version** 2021.4 **What is the current bug behavior?** While for the first seconds of run the output is correct: ``` Back Off! I just backed up step7_mol.xtc to ./#step7_mol.xtc.2# Reading frame 20 time 3501000.000 -> frame 20 time 1000.000 ``` Some seconds later user will simply read this in the terminal: ``` > frame 660 time 33000.000 -> frame 600 time 30000.000 ``` Instead of the equivalence between the original times and the new ones **What did you expect the correct behavior to be?** It should show the times from the original file and the new ones, as it does during the first seconds of run.