[NCP] nc-update-nextcloud fails with "free space check failed"

I run ncp-config > TOOLS > nc-update-nextcloud and enter 0 for version. Output-

Running nc-update-nextcloud
Current   Nextcloud version
Available Nextcloud version 15.0.5
Download Nextcloud 15.0.5...
Back up current instance...
check free space...
free space check failed. Need 110462852 Bytes
Maintenance mode disabled
Error backing up
Clean up...
Done. Press any key...

root@5a399d7ed969:/# df -h
Filesystem      Size  Used Avail Use% Mounted on
overlay         144G  109G   28G  80% /
tmpfs            64M     0   64M   0% /dev
tmpfs          1002M     0 1002M   0% /sys/fs/cgroup
/dev/sda1       144G  109G   28G  80% /data
shm              64M     0   64M   0% /dev/shm
tmpfs          1002M     0 1002M   0% /proc/asound
tmpfs          1002M     0 1002M   0% /proc/scsi
tmpfs          1002M     0 1002M   0% /sys/firmware

root@5a399d7ed969:/# ncp-check-updates 

NextCloudPi v1.9.1 is up to date

110462852 Bytes should mean around ~100M and I do have 28G free. What might be wrong?

If it helps, I installed NCP using IP= docker-compose -f docker-compose-armhf.yml up -d few months back and it has been working well since then. I do not have automatic backups configured in ncp-config.