Size the binary logs
The provided configuration (max_binlog_size=500M in the MariaDB settings) allows you to configure the maximal size of the binary log files before rotating. The smaller the size, the more often rotations will occur, which will slow down replication. The advantage is a more efficient purge process. The bigger the size, the less often rotations will occur, but the disk may be filled with old logs.
According to our experiences, a size less than 8K does stop replication completely under heavy load, because the slave keeps rotating the logs.