Bad write log efficiency, strange broken relationships

I recently switched galera synchronization method from rsync to mariabackup which greatly reduced CPU usage on our DB servers and also increased the innodb_log_file_size to 2G from about 600M or so. Since then (might be a coincidence) I started getting a lot of aborted connection errors and bad log write efficiency. I initially thought it had something to do with wait_timeout (which we set to 5 since our application has to be very fast ) and raised it to 60 as well as max_allowed_packet to 2G. But even after that the errors still remained. And AlertManager raises host crash errors almost hourly. [--] Skipped version check for MySQLTuner script [OK] Logged in using credentials passed on the command line [OK] Currently running supported MySQL version 10.4.14-MariaDB-1:10.4.14+maria~focal-log [OK] Operating on 64-bit architecture -------- Log file Recommendations ------------------------------------------------------------------ [!!] Log file doesn't exist -------- Storage Engine Statistics ----------------------------------------------------------------- [--] Status: +Aria +CSV +InnoDB +MEMORY +MRG_MyISAM +MyISAM +PERFORMANCE_SCHEMA +SEQUENCE [--] Data in InnoDB tables: 16.3G (Tables: 150) [OK] Total fragmented tables: 0 -------- Analysis Performance Metrics -------------------------------------------------------------- [--] innodb_stats_on_metadata: OFF [OK] No stat updates during querying INFORMATION_SCHEMA. -------- Security Recommendations ------------------------------------------------------------------ [OK] There are no anonymous accounts for any database users [!!] User 'mariadb.sys@localhost' has no password set. [!!] User 'developer@%' does not specify hostname restrictions. [--] There are 620 basic passwords in the list. -------- CVE Security Recommendations -------------------------------------------------------------- [OK] NO SECURITY CVE FOUND FOR YOUR VERSION -------- Performance Metrics ----------------------------------------------------------------------- [--] Up for: 4h 56m 41s (1M q [64.284 qps], 33K conn, TX: 758M, RX: 166M) [--] Reads / Writes: 40% / 60% [--] Binary logging is enabled (GTID MODE: OFF) [--] Physical Memory : 54.9G [--] Max MySQL memory : 46.1G [--] Other process memory: 0B [--] Total buffers: 19.2G global + 26.9M per thread (1000 max threads) [--] P_S Max memory usage: 623M [--] Galera GCache Max memory usage: 128M [OK] Maximum reached memory usage: 20.7G (37.77% of installed RAM) [OK] Maximum possible memory usage: 46.1G (83.90% of installed RAM) [OK] Overall possible memory usage with other process is compatible with memory available [OK] Slow queries: 4% (55K/1M) [OK] Highest usage of available connections: 3% (36/1000) [!!] Aborted connections: 10.61% (3560/33563) [OK] Query cache is disabled by default due to mutex contention on multiprocessor machines. [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 3 sorts) [OK] No joins without indexes [OK] Temporary tables created on disk: 12% (13 on disk / 107 total) [OK] Thread cache hit rate: 99% (69 created / 33K connections) [OK] Table cache hit rate: 97% (290 open / 296 opened) [OK] table_definition_cache(400) is upper than number of tables(313) [OK] Open file limit used: 0% (58/16K) [OK] Table locks acquired immediately: 100% (686 immediate / 686 locks) [OK] Binlog cache memory access: 100.00% (586009 Memory / 586009 Total) -------- Performance schema ------------------------------------------------------------------------ [--] Memory used by P_S: 623.7M [--] Sys schema isn't installed. -------- ThreadPool Metrics ------------------------------------------------------------------------ [--] ThreadPool stat is enabled. [--] Thread Pool Size: 14 thread(s). [--] Using default value is good enough for your version (10.4.14-MariaDB-1:10.4.14+maria~focal-log) -------- MyISAM Metrics ---------------------------------------------------------------------------- [!!] Key buffer used: 18.3% (6M used / 33M cache) [!!] Cannot calculate MyISAM index size - re-run script as root user -------- InnoDB Metrics ---------------------------------------------------------------------------- [--] InnoDB is enabled. [--] InnoDB Thread Concurrency: 0 [OK] InnoDB File per table is activated [OK] InnoDB buffer pool / data size: 19.0G/16.3G [OK] Ratio InnoDB log file size / InnoDB Buffer pool size: 2.0G * 2/19.0G should be equal to 25% [OK] InnoDB buffer pool instances: 19 [--] Number of InnoDB Buffer Pool Chunk : 152 for 19 Buffer Pool Instance(s) [OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances [OK] InnoDB Read buffer efficiency: 100.00% (12044117752 hits/ 12044442245 total) [!!] InnoDB Write Log efficiency: 87.27% (874238 hits/ 1001803 total) [OK] InnoDB log waits: 0.00% (0 waits / 127565 writes) -------- AriaDB Metrics ---------------------------------------------------------------------------- [--] AriaDB is enabled. [OK] Aria pagecache size / total Aria indexes: 128.0M/312.0K [OK] Aria pagecache hit rate: 99.5% (2K cached / 14 reads) -------- TokuDB Metrics ---------------------------------------------------------------------------- [--] TokuDB is disabled. -------- XtraDB Metrics ---------------------------------------------------------------------------- [--] XtraDB is disabled. -------- Galera Metrics ---------------------------------------------------------------------------- [--] Galera is enabled. [--] GCache is using 0B [--] CPU core detected : 14 [--] wsrep_slave_threads: 32 [OK] wsrep_slave_threads is equal to 2, 3 or 4 times number of CPU(s) [OK] gcs.fc_limit should be equal to 5 * wsrep_slave_threads [--] wsrep parallel slave can cause frequent inconsistency crash. [OK] gcs.fc_limit is equal to 5 * wsrep_slave_threads [OK] gcs.fc_factor is equal to 0.8 [OK] Flow control fraction seems to be OK (wsrep_flow_control_paused1 and command"Sleep"; To try debugging slow queries but it's always an empty set yet the tuner reports over 5k slow queries (the slow query time is set to 5s).