mariabackup -prepare step on increment backup failed

Hi,
Got an error with mariabackup during -prepare step on the increment backup.

Distribution:
Ver 15.1 Distrib 10.6.4-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2

I have a full backup without any partitioned tables and the increment backup has table pertionned.

1. --------------
2. full backup
3. --------------
   mariabackup --defaults-file=/etc/mysql/my.cnf \
   --backup \
   --binlog-info \
   --target-dir=/var/lib/mysql/backup/full/ \
   ...

1. ------------------
2. incremental backup
3. -------------------
   mariabackup --defaults-file=/etc/mysql/my.cnf \
   --backup \
   --binlog-info \
   --target-dir=/var/lib/mysql/backup/inc1/ \
   --incremental-basedir=/var/lib/mysql/backup/full/ \
   ....

1. ----------------------
2. 1- Prepare on full backup is OK
3. -----------------------
   mariabackup --defaults-file=/etc/mysql/my.cnf \
   > --prepare \
   > --target-dir=/var/lib/mysql/backup/full
   mariabackup based on MariaDB server 10.6.4-MariaDB debian-linux-gnu (x86_64)
   [00] 2021-10-22 11:03:01 cd to /var/lib/mysql/backup/full/
   [00] 2021-10-22 11:03:01 open files limit requested 1024, set to 1024
   [00] 2021-10-22 11:03:01 This target seems to be not prepared yet.
   [00] 2021-10-22 11:03:01 mariabackup: using the following InnoDB configuration for recovery:
   [00] 2021-10-22 11:03:01 innodb_data_home_dir = .
   [00] 2021-10-22 11:03:01 innodb_data_file_path = ibdata1:128M:autoextend
   [00] 2021-10-22 11:03:01 innodb_log_group_home_dir = .
   [00] 2021-10-22 11:03:01 InnoDB: Using Linux native AIO
   [00] 2021-10-22 11:03:01 Starting InnoDB instance for recovery.
   [00] 2021-10-22 11:03:01 mariabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)
   2021-10-22 11:03:01 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
   2021-10-22 11:03:01 0 [Note] InnoDB: Number of pools: 1
   2021-10-22 11:03:01 0 [Note] InnoDB: Using SSE4.2 crc32 instructions
   2021-10-22 11:03:01 0 [Note] InnoDB: Using Linux native AIO
   2021-10-22 11:03:01 0 [Note] InnoDB: Initializing buffer pool, total size = 104857600, chunk size = 104857600
   2021-10-22 11:03:01 0 [Note] InnoDB: Completed initialization of buffer pool
   2021-10-22 11:03:01 0 [Note] InnoDB: Starting crash recovery from checkpoint LSN=42161,42161
   [00] 2021-10-22 11:03:01 Last binlog file , position 0
   [00] 2021-10-22 11:03:01 completed OK!

1. ----------------------
2. 2 - Prepare on inc backup failed with this error:
3. ----------------------
   mariabackup --defaults-file=/etc/mysql/my.cnf \
   > --prepare \
   > --target-dir=/var/lib/mysql/backup/full \
   > --incremental-dir=/var/lib/mysql/backup/inc1
   mariabackup based on MariaDB server 10.6.4-MariaDB debian-linux-gnu (x86_64)
   [00] 2021-10-22 11:06:15 incremental backup from 42161 is enabled.
   [00] 2021-10-22 11:06:15 cd to /var/lib/mysql/backup/full/
   [00] 2021-10-22 11:06:15 open files limit requested 1024, set to 1024
   [00] 2021-10-22 11:06:15 Renaming /var/lib/mysql/backup/inc1//KANNEL/DLR#P#2018_06_08.new to ./KANNEL/DLR#P#2018_06_08.ibd

mariabackup: Error on rename of '/var/lib/mysql/backup/inc1//KANNEL/DLR#P#2018_06_08.new' to './KANNEL/DLR#P#2018_06_08.ibd' (errno: 20 "Not a directory")
[00] FATAL ERROR: 2021-10-22 11:06:15 Can't rename /var/lib/mysql/backup/inc1//KANNEL/DLR#P#2018_06_08.new to ./KANNEL/DLR#P#2018_06_08.ibd errno 2

1. file exist
   $ ls /var/lib/mysql/backup/inc1//KANNEL/DLR#P#2018_06_08.new
   /var/lib/mysql/backup/inc1//KANNEL/DLR#P#2018_06_08.new