plot crashes

[oliverzh]

On one ubuntu 18, the plot process keeps crash without any errors. Below is an example.

Working Directory: /mnt/cache3/
Working Directory 2: /mnt/cache3/
Plot Name: plot-k32-2021-06-18-13-24-ad76f5be9e633f6eaf4e10684aeff81ec61ce8dfe3bc0896d83c96220ad70b59
[P1] Table 1 took 66.5353 sec
[P1] Table 2 took 363.733 sec, found 4294893280 matches
[P1] Table 3 took 506.629 sec, found 4294798107 matches
[P1] Table 4 took 616.065 sec, found 4294553422 matches
[P1] Table 5 took 599.038 sec, found 4294073255 matches
[P1] Table 6 took 561.572 sec, found 4293245851 matches
[P1] Table 7 took 386.612 sec, found 4291552558 matches
Phase 1 took 3100.21 sec
[P2] max_table_size = 4294967296
[P2] Table 7 scan took 22.3766 sec
[P2] Table 7 rewrite took 67.6218 sec, dropped 0 entries (0 %)
[P2] Table 6 scan took 128.556 sec
[P2] Table 6 rewrite took 217.375 sec, dropped 581503173 entries (13.5446 %)
[P2] Table 5 scan took 128.726 sec
[P2] Table 5 rewrite took 207.618 sec, dropped 762190352 entries (17.7498 %)
[P2] Table 4 scan took 126.879 sec
[P2] Table 4 rewrite took 203.918 sec, dropped 829000775 entries (19.3035 %)
[P2] Table 3 scan took 125.566 sec
[P2] Table 3 rewrite took 203.055 sec, dropped 855215318 entries (19.9128 %)
[P2] Table 2 scan took 125.594 sec
[P2] Table 2 rewrite took 202.517 sec, dropped 865644873 entries (20.1552 %)
Phase 2 took 1765.03 sec
Wrote plot header with 268 bytes
[P3-1] Table 2 took 134.683 sec, wrote 3429248407 right entries
[P3-2] Table 2 took 109.828 sec, wrote 3429248407 left entries, 3429248407 final
[P3-1] Table 3 took 147.555 sec, wrote 3439582789 right entries

There are three plot processes running on one ssd each. Maybe once a day or two, there would be one processes missing. How do I troubleshoot what caused the crash?