Problems with WebDAV in iOS

Hello everyone.

I’m having a problem with a iOS app. The error:

"Read Folder WebDAV : [items NULL] please fix"

It does not load my folders and present that error. Sometimes the error disappear and I can see the folders normally, but sometimes…

I use:
Nextcloud Version: 11.0.1 (stable)
Nextcloud App Version: 2.16(00012)
iOS Version: 10.2.1

Others services like calendar and news it work perfectly. Sync and folders in my desktop app also it work.

Can anyone help me?