Output of `df` with: `df: /run/user/1000/doc: Operation not permitted`

I’m using Silverblue and after some weeks … I perceive the following error in df output:

$ df -h
df: /run/user/1000/doc: Operation not permitted
Filesystem                            Size  Used Avail Use% Mounted on
devtmpfs                              7,8G     0  7,8G   0% /dev
tmpfs                                 7,8G   84K  7,8G   1% /dev/shm
tmpfs                                 7,8G  9,9M  7,8G   1% /run
/dev/mapper/fedora-root                68G   22G   43G  34% /sysroot
tmpfs                                 7,8G  108K  7,8G   1% /tmp
/dev/mapper/fedora-home                33G   16G   16G  50% /var/home
/dev/sda1                             976M  228M  682M  26% /boot
tmpfs                                 1,6G  212K  1,6G   1% /run/user/1000

Someone knows what is happening?

Maybe this is related somehow to Flatpak?

I have received the same message: df: /run/user/1000/doc: Operation not permitted

This isn’t a problem.
The explanation about this behavior as some hints to overcome problems with orphaned files at /run/user/1000/doc here: