Can't update: free space check failed - ncp-snapshots apparent size is 1.7TB on 150GB HDD

Nextcloud version:
NextcloudPi version: v1.52.2
Operating system and version: Debian GNU/Linux 11. 5.10.0-23-arm64 (aarch64)

I can’t update my NextCloud version because the updater says I need 1.5TB free space on a 150GB HDD.

Here’s the log for nc-update-nextcloud

[ nc-update-nextcloud ] (Tue Jul 25 21:40:16 AEST 2023)
Current Nextcloud version
Available Nextcloud version 26.0.3
Download Nextcloud 26.0.3...
Back up current instance...
check free space...
free space check failed. Need 1914691427553 Bytes
Maintenance mode already disabled
Error backing up
Clean up...

Ran sudo ncdu and my folder /var/www/nextcloud/ncp-snapshots is taking up 1.7TB but it’s only on a 150GB HDD.

For comparison, here’s the output of df -h:

Filesystem      Size  Used Avail Use% Mounted on
udev            3.9G     0  3.9G   0% /dev
tmpfs           795M  1.5M  793M   1% /run
/dev/vda2       149G   66G   81G  45% /
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
/dev/vda1       512M  5.9M  506M   2% /boot/efi
tmpfs           795M   72K  795M   1% /run/user/116
tmpfs           795M   56K  795M   1% /run/user/1000

Ordinarily that wouldn’t really bother me, except that the free space check script of ncp-update-nextcloud command views the size of the snapshots folder in the same way that ncdu does, not how df views it.

I was able to update from NC 24 to 25 to 26 by erasing the snapshots and re-running the updater, but that kind of defeats the purpose of the backups.

Is there any way I can update without deleting all my snapshots?