Concatenate two trajectories

GROMACS version:
GROMACS modification: Yes/No
Here post your question I have concatenated two trajectories but teh output file is terminating at 81 ns. But the log file clearly explains that teh simulation is completed till 500ns.

commmand used- gmx_mpi trjcat -f md_0_1.trr traj.trr -o fixed.trr

      md_0_1.trr        0.000 ps       10.000 ps
              old.trr    24980.000 ps       10.000 ps

Error got - Continue writing frames from md_0_1.trr t=0 ps, frame=0
→ frame 2490 time 24900.000 ps → frame 2000 time 20000.000 ps
Reading frame 0 time 24980.000
lasttime 24970

Continue writing frames from old.trr t=24980 ps, frame=2498
→ frame 8100 time 81000.000 ps → frame 7500 time 75000.000 ps

Last frame written was 8101, time 81010.000000 ps

gcq#424: “Consistently separating words by spaces became a general custom about the tenth century A.D., and lasted until about 1957, when FORTRAN abandoned the practice.” (Sun FORTRAN Reference Manual)

Kindly help and thanks in advance .