Steps to reproduce:

1. Probably no direct way to reproduce these crashes. They began yesterday and affect both proxies every 1 to 6 hours, randomly. Maybe you can spot something in the backtrace.
2. This is on version 5.4.9.

Result:

  6283:20220413:100225.364 slow query: 19.691975 sec, "select id,itemid,clock,ns,timestamp,source,severity,value,logeventid,state,lastlogsize,mtime,flags from proxy_history where id>6129512444 order by id limit 1000"
  6275:20220413:100225.585 14: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](zbx_backtrace+0x4e) [0x56154c939eb8]
  6275:20220413:100225.586 13: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](__zbx_mem_malloc+0x180) [0x56154c934777]
  6275:20220413:100225.586 12: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](+0x1439d8) [0x56154c8b59d8]
  6275:20220413:100225.586 11: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](zbx_hashset_insert_ext+0x12f) [0x56154c9e8a7a]
  6275:20220413:100225.586 10: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](zbx_hashset_insert+0x2d) [0x56154c9e8949]
  6275:20220413:100225.586 9: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](+0x143d2c) [0x56154c8b5d2c]
  6275:20220413:100225.587 8: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](+0x144432) [0x56154c8b6432]
  6275:20220413:100225.587 7: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](dc_flush_history+0x49) [0x56154c8b5944]
  6275:20220413:100225.587 6: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](preprocessing_manager_thread+0x508) [0x56154c806127]
  6275:20220413:100225.587 5: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](zbx_thread_start+0x37) [0x56154c93f5ad]
  6275:20220413:100225.588 4: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](MAIN_ZABBIX_ENTRY+0xe65) [0x56154c7c30dc]
  6275:20220413:100225.588 3: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](daemon_start+0x2f5) [0x56154c939a8b]
  6275:20220413:100225.588 2: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](main+0x29e) [0x56154c7c2218]
  6275:20220413:100225.588 1: /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7) [0x7f4c17487c87]
  6275:20220413:100225.588 0: /usr/sbin/zabbix_proxy: preprocessing manager #1 [queued 20, processed 6394 values, idle 4.424181 sec during 5.109184 sec](_start+0x2a) [0x56154c7c108a]
  6279:20220413:100226.503 cannot read preprocessing service request
  6277:20220413:100226.504 cannot read preprocessing service request
  6254:20220413:100226.504 One child process died (PID:6275,exitcode/signal:1). Exiting ...
  6276:20220413:100226.505 cannot read preprocessing service request
  6498:20220413:100226.688 cannot write to IPC socket: Broken pipe
  6498:20220413:100226.688 cannot send data to preprocessing service
zabbix_proxy [6254]: Error waiting for process with PID 6275: [10] No child processes
  6254:20220413:100231.384 syncing history data...

Expected:
See screenshot....
See attached patch file...