rsync refuses to exclude directory

I'm trying to make a OS backup with rsync and have put this into crontab. which by itself works great, but for some reason it refuses to take /export into account while looking at the excludes...

0 2 * * 0 rsync -aAXv / --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found","/export/*"} /media/backup-disk/server-backup/ >/dev/null 2>&1

It does exclude all other folders from the backup though.

The general reason I also want to exclude this /export/* is due to the fact that this backup disk is also mounted as bind to /export due to a nfs share of the disk to a remote server.

Due to the fact that is does include /export/* i keep on ending up with my disk being full due to a loop in my rsync as it starts to backup the disk itself to itself (/export/backup-disk/ -> /media/backup-disk/server-backup)

the mount of my /media/backup-disk to export is as followed in /etc/fstab:

/media/backup-disk       /export/backup-disk       none       bind  0  0 

So my general question is, why is it including /export/* while it is inside the exclude option of rsync, and how do I fix this?

Edit:

the result of a dry-run with --stats --progress (without redirecting stout en stin to /dev/null):

sudo rsync -aAXv --stats --progress / --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found","/export/*"} /media/backup-disk/test/ > /media/backup-disk/test.txt 

cat /media/backup-disk/test.txt | grep -A1 export/        
export/
home/
--
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/__init__.py
          9,060 100%   38.98kB/s    0:00:00 (xfr#17141, ir-chk=1174/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/day.py
         12,609 100%   54.24kB/s    0:00:00 (xfr#17142, ir-chk=1173/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/export_custom_job.py
         12,034 100%   51.77kB/s    0:00:00 (xfr#17143, ir-chk=1172/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/job.py
          8,970 100%   38.59kB/s    0:00:00 (xfr#17144, ir-chk=1171/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/__pycache__/
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/__pycache__/__init__.cpython-38.pyc
          8,809 100%   37.90kB/s    0:00:00 (xfr#17145, ir-chk=1169/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/__pycache__/day.cpython-38.pyc
         12,206 100%   52.28kB/s    0:00:00 (xfr#17146, ir-chk=1168/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/__pycache__/export_custom_job.cpython-38.pyc
         11,859 100%   50.79kB/s    0:00:00 (xfr#17147, ir-chk=1167/22834)
home/user/.local/lib/python3.8/site-packages/twilio/rest/bulkexports/v1/export/__pycache__/job.cpython-38.pyc
          9,302 100%   39.84kB/s    0:00:00 (xfr#17148, ir-chk=1166/22834)
...

This indicates that it does exclude export, but still somehow I keep finding my disk being full every time the cron runs due to it still copying stuff inside /export to my server-backup directory...

another thing I forgot to mention here is that I initially thought it could be an issue of forgetting /export/* at first, added it later on to the cron, but forgot to reboot (so no cron schedular reboot), but even after a reboot, it still manages to copy /export/* with the cron. Also seems a bit stupid that it would be needed to reboot as it should be able to handle edits to the cron every time it needs to run the command from the cron, but wanted to be sure that it didn't get solved after a reboot...

Seems the problem was indeed like @steeldriver mentioned, the way that crons are run (in sh instead of bash or zsh or any other shell). That made it incompatible with the brace expansion of the exclude list.

The tip on adding the shell to the cron didn't fix this issue, but putting the command inside a script and running the script did fix the issue.

So I now have a script which has the following:

#!/bin/zsh

rsync -aAXv --stats --progress / --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found","/export/*"} /media/backup-disk/test  > /dev/null 2>&1

and the cron as following to make it run every sunday night at 2am:

0 2 * * 0 /opt/scripts/rsync-os-backup