Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

[sissiautumn]

Please help me figure out this problem (Ubuntu 18.04 system). The axisem just calculated 49% and then segmentation faults appeared (every time). Thanks in advance.

.......
time step: 5500; t= 787.69 s ( 43.8%)
time step: 5600; t= 802.01 s ( 44.6%)
time step: 5700; t= 816.33 s ( 45.3%)
time step: 5800; t= 830.65 s ( 46.1%)
time step: 5900; t= 844.97 s ( 46.9%)
time step: 6000; t= 859.29 s ( 47.7%)
time step: 6100; t= 873.62 s ( 48.5%)
time step: 6200; t= 887.94 s ( 49.3%)

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0 0x7f58064312da in ???
#1 0x7f5806430503 in ???
#2 0x7f580588ef1f in ???
#3 0x7f5805c49bd8 in ???
#4 0x563eaaad94e1 in c_wait_for_io
at /home/dell/software/axisem-master/SOLVER/pthread.c:55
#5 0x563eaa775cf5 in __nc_routines_MOD_nc_rec_checkpoint
at /home/dell/software/axisem-master/SOLVER/nc_routines.F90:599
#6 0x563eaa7bc448 in dump_stuff
at /home/dell/software/axisem-master/SOLVER/time_evol_wave.F90:1144
#7 0x563eaa808070 in sf_time_loop_newmark
at /home/dell/software/axisem-master/SOLVER/time_evol_wave.F90:498
#8 0x563eaa8081d6 in __time_evol_wave_MOD_time_loop
at /home/dell/software/axisem-master/SOLVER/time_evol_wave.F90:238
#9 0x563eaa92d991 in axisem
at /home/dell/software/axisem-master/SOLVER/main.f90:92
#10 0x563eaa92dbcc in main
at /home/dell/software/axisem-master/SOLVER/main.f90:25

mpirun noticed that process rank 1 with PID 0 on node dell-Precision-7920-Tower exited on signal 11 (Segmentation fault).

[sissiautumn]

The error disappears after two weeks break, I didn't do anything :)
If I change the length from 1800 s to 800 s, the IEEE_UNDERFLOW_FLAG problem shows up.