Clean deploy of NextcloudPi — Log spammed with errors: Unable to create temporary file, Check permissions in temporary files directory

I’ve just deployed NCP and the only operation I’ve done from ncp-web is moving the datadir to my external USB mounted HDD. The external HDD is mounted regularly by fstab and not by NCP automount feature.

I noticed the the logs are filled with errors like:

Unable to create temporary file, Check permissions in temporary files directory. at /var/www/nextcloud/apps/files_external/3rdparty/icewind/streams/src/Wrapper.php#91

curl_exec(): Unable to create temporary file, Check permissions in temporary files directory. at /var/www/nextcloud/3rdparty/guzzlehttp/guzzle/src/Handler/CurlHandler.php#40

I don’t know if it is related but I can’t see any app available as NCP shows me the message " No apps found for your version".

Are the two things related? And anyway should I be worried by this error?

In the configuration I correctly see (ugreen is my mountpoint of the HDD):

tempdirectory /mnt/ugreen/ncp/tmp

Edit
The user permissions should be correct too as the folders are owned with write permission by drwxr-xr-x www-data.

Also the similar post is due to an update of the ncp instance and related to uploading files so I I’m not sure my issue is related.