Iphone nextcloud app is not uploading all the files

As a newcomer to Nextcloud, I recently set up Nextcloud on my Raspberry Pi 4 and connected an external SSD to it. I have two phones: an iPhone and a Samsung. I installed the Nextcloud client apps on both devices and linked them to my Nextcloud account. Interestingly, the Android app successfully uploaded all my files, but the iPhone app only uploaded partial files. I attempted to use the auto-upload feature again, but unfortunately, it still didn’t work as expected.
here are the snapshot

is this problem with iphone app or at the backend side? Any suggestion as to what i should do?

For iPhone, if you open the Nextcloud app, it should start to synchronize. Sometime when it is not running in the background, for me it is not reliably syncing when I am not opening the app from time to time. However, I don’t see the problem with partial uploads.

In such a case, I’d check the server logfiles, if there is a timeout or something after a certain amount of time. It could also be a hint, if it fails after a fixed amount of time or after a fixed amount of data transferred.