[6.12.13] Hardlinking issues when the source is on the Array

root@Tower:~# mkdir '/mnt/user/media/test_destination'
root@Tower:~# ln '/mnt/user/media/test_source/source.txt' '/mnt/user/media/test_destination/source.txt'
ln: failed to create hard link '/mnt/user/media/test_destination/source.txt' => '/mnt/user/media/test_source/source.txt': Is a directory
root@Tower:~# ln '/mnt/user/media/test_source/source.txt' '/mnt/user/media/test_destination/source.txt'
root@Tower:~# ls -al '/mnt/user/media/test_destination'
total 0
drwxrwxrwx 1 root   root   0 Nov 27 19:14 ./
drwxrwxrwx 1 nobody users 70 Nov 27 19:14 ../
-rw-rw-rw- 2 root   root   0 Nov 27 19:11 source.txt
root@Tower:~# 

source.txt is on the Array. When I first call the hardlinking command, I get the "Is a directory" error, but if I call the command immediately again, it works. If I delete the file from the destination location and link again, it works. But if I delete the destination folder, make a new one, then the error appears again.

The error doesn't appear if the source is on the cache disk (Primary Storage).

My disks are formatted as BTRFS.

Unraid version 6.12.13