Can't update NextCloudPi v0.56.21 to v1.10.6

NextcloudPi version: 0.56.21 (latest version is 1.10.6)
NextCloudPi image: NextCloudPi_03-18-18
Nextcloud version:
Distribution: Raspbian GNU/Linux 9
raspi-config is the newest version (20190219).

After a 287-day uptime and reading about NC15.0.5, I thought of upgrading my home file server. About time, huh?

Both sudo ncp-update and sudo ncp-config downloaded package files but returned cp cannot create regular file '/usr/local/bin/noip2': Text file busy

Looks like these commands ended up in duplicating most items in the WebUI’s tools panel, except from: SSH, UFW, nc-hdd-monitor, nc-hdd-test, nc-info, nc-maintenance, nc-prettyURL, nc-previews-auto, nc-previews, nc-restore-snapshots (but 2x nc-restore), nc-trusted-domains, nc-update-nc-apps-auto, nc-wifi, no-ip, samba, spBYN, unattended-upgrades.

Remember reading that upgrading from NC13 to NC15 was not possible due to major versions released in between.

Thanks a lot in advance for your help. Please ask if you need more info.