Error in MariaBackup incremental backup

I have a backup script, which takes a full backup 1 day of the week followed by incremental backups for the following days.

Command ran was:

mariabackup \
--backup \
--parallel=8 \
--user=$mysql_user \
--password=$mysql_pass \
--no-timestamp \
--compress \
--compress-threads=8 \
--incremental-basedir=$last_backup \
--socket=$socket \
--defaults-group="mysqld$instance" \
--target-dir=$inc_backup_path 2> $logfile_i

Previously we had this working using the command:

innobackupex \
--parallel=8 \
--user=$mysql_user \
--password=$mysql_pass \
--no-timestamp \
--compress \
--compress-threads=8 \
--incremental \
--incremental-basedir=$last_backup \
--socket=$socket \
--defaults-group="mysqld$instance" \
$inc_backup_path 2> $logfile_i

Any ideas?

We previously were unable to perform backups at all until the 10.2.8 version of mariabackup.

Our tables range in size from 1-2GB to upwards of a 1T.