Is there a solution for mariadb-backup? I haven't been able to sync nodes or create a backup for the last 18 months on the 10.11 version.

mariadb-backup could abort with the misleading error "Was only able to copy log from X to Y, not Z; try increasing innodb_log_file_size" even when the redo log was intact and far from full. The log copier could read a partially written tail block that still parsed with a valid CRC, advancing its parse position into the middle of a mini-transaction, after which it never caught up to the target LSN. The copier now parses the redo log only up to the server's durably flushed LSN (Innodb_lsn_flushed), and re-reads those bytes on a later pass.