I see error in Zabbix frontend: "Zabbix server is not running. The information displayed may not be current"
And in /var/log/zabbix_server.log I see server start and stop bouncing endlessly:
562947:20260302:111203.778 server #2 started configuration syncer #1
562947:20260302:111204.260 __mem_malloc: skipped 0 asked 24 skip_min 18446744073709551615 skip_max 0
562947:20260302:111204.260 === memory statistics for configuration cache ===
562947:20260302:111204.260 min chunk size:          0 bytes
562947:20260302:111204.260 max chunk size:          0 bytes
562947:20260302:111204.260 memory of total size 28074088 bytes fragmented into 342498 chunks
562947:20260302:111204.260 of those,          0 bytes are in        0 free chunks
562947:20260302:111204.260 of those,   28074088 bytes are in   342498 used chunks
562947:20260302:111204.260 of those,    5479952 bytes are used by allocation overhead
562947:20260302:111204.260 ================================
562947:20260302:111204.260 === Backtrace: ===
562947:20260302:111204.262 11: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](zbx_backtrace+0x3b) [0x56466456b10b]
562947:20260302:111204.262 10: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](__zbx_shmem_malloc+0x68) [0x564664483e58]
562947:20260302:111204.262 9: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](+0x288251) [0x5646643e6251]
562947:20260302:111204.262 8: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](zbx_dc_sync_configuration+0x4fdd) [0x564664411c8d]
562947:20260302:111204.262 7: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](dbconfig_thread+0xeb) [0x56466424917b]
562947:20260302:111204.262 6: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](zbx_thread_start+0x20) [0x56466448e8a0]
562947:20260302:111204.262 5: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](+0xe1b8b) [0x56466423fb8b]
562947:20260302:111204.262 4: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](MAIN_ZABBIX_ENTRY+0x1056) [0x5646642412f6]
562947:20260302:111204.262 3: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](main+0x379) [0x564664235249]
562947:20260302:111204.262 2: /lib/x86_64-linux-gnu/libc.so.6(+0x29ca8) [0x7f5b3b695ca8]
562947:20260302:111204.262 1: /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x85) [0x7f5b3b695d65]
562947:20260302:111204.262 0: /usr/sbin/zabbix_server: configuration syncer [syncing configuration](_start+0x21) [0x56466423c381]
562947:20260302:111204.262 file:dbconfig.c,line:264 __zbx_shmem_malloc(): out of memory (requested 16 bytes)
562947:20260302:111204.262 file:dbconfig.c,line:264 __zbx_shmem_malloc(): please increase CacheSize configuration parameter
562942:20260302:111204.272 One child process died (PID:562947,exitcode/signal:1). Exiting ...
562944:20260302:111204.272 HA manager has been paused
562944:20260302:111205.881 HA manager has been stopped
562942:20260302:111205.884 Zabbix Server stopped. Zabbix 7.4.7 (revision b033beafb23).