iTunes backup includes external storage

[doomi]

For a year I wondered why my iTunes backup of my iPhone is using way more space than my iPhone has storage (128GB iPhone, backup usage 400GB).
I just disabled external storage (Google drive) on my Nextcloud server due to issue #398, and now my backups are the correct size again.
Conclusion: iTunes backup downloads and backs up the linked external storages!

Expected behaviour

iTunes backup should only backup app setting, but no files, cache or external storage.

Actual behaviour

I have Google drive as external storage configured (300GB used) on Nextcloud server. iPhone 6s with 128GB, about 100GB used. the iTunes backup takes two days and uses 400GB, as it downloads and backs up my external storage (Google drive).

Steps to reproduce

Enable external storage plugin on server, configure Google Drive, backup iPhone with iTunes.

iOS version

11.2.1

App version

2.19.1.00002

Server configuration

No access to server configuration or logs

Nextcloud version: (see Nextcloud admin page)
12.0.5

[doomi]

I‘m closing this issue because I hope #411 fixed this one, too.
And I don’t have the possibility right now to test/reproduce it (no notebook for testing)