space is full even though i deleted a complete share

This is information about the file system, but not errors (which would be in system.log, kernel.log, and dmesg.log).

That said, I am seeing something I don't understand in the qgroup section

=== qgroup /data ===
qgroupid         rfer         excl     max_rfer 
--------         ----         ----     -------- 
0/274           0.00B    955.76GiB         none 
0/7483      862.76GiB    803.88GiB         none 

I'd expect to see these two IDs in the subvolume list, but I am not seeing them there. 

Perhaps someone else ( maybe rn_enthusiast ) can also take a look?

BTRFS is reporting the used space as almost at total capacity.

Label: '0a43aafa:data' uuid: 67872479-fb0e-493c-b57a-5e0b27beba2f
Total devices 1 FS bytes used 2.53TiB
devid 1 size 2.72TiB used 2.54TiB path /dev/md127

Some peculiar things here...

What are these shares here? Do you recognize these? Some of them take significant space according to the quota reports.

- ID 880 gen 426199 top level 5 path שיעורים
- ID 2334 gen 425322 top level 5 path קטלוג-ראשוני
- ID 4989 gen 425296 top level 5 path קטלוג_ספרן

What is the share name that you are having particular issues with?

It also looks like quotas are wack here. Referencing many subvolume IDs that don't exist. And other places it is reporting fictitious subvolumes as max BRTFS theoretical capacity :) Like this:

=== qgroup /data ===
qgroupid rfer excl max_rfer
-------- ---- ---- --------
0/1922 16.00EiB 16.00EiB none
0/2332 16.00EiB 16.00EiB none
0/3998 16.00EiB 16.00EiB none
0/7321 16.00EiB 16.00EiB none

Can you please start by disabling quotas?
Go to admin web page and navigate to: "System" > "Volumes" > Click the cog-wheel next to your raid Volume > select "Settings".
Once in Setting, select "Summary" on the left hand side. Here you Un-tick the box that says: "Quota" > Click "Apply" at the bottom.

Afterwards, give the NAS a reboot and see what happens to the capacity problem.

After reboot, please post output of these commands:

btrfs fi sh /data
btrfs fi df /data
btrfs subv list /data
du -hd1 /data
btrfs qgroup show /data (this command should fail, it is just to check quotas are disabled).

Thanks