iOS 11 woes

New iXpand 128gb, iPhone 8+, iOS 11.

Device is recognized, app started, backup began, and then app continually restarts itself.

Phone was power-cycled off and on after app installed and again after error appeared. No joy.

do you have the latest release of iOS 11 ver 11.0.1? does the drive work normally in a computer or with other iOS devices? 

I would try backing up any content on the drive and formatting using exFAT file system and see if the issue still happens. It would be helpful to know if the same thing occurs on other iOS devices. 

I have iPhone 7 iOS 11.0.1 and backup is working form me. 

iOS v 11.0.1 installed.

No change.

Also occurs on iPad 5th gen (latest 2017 model) running 11.0.1.

No change after reformatting as suggested.

since it is happening on multiple devices it may be the iXpand itself. you could try exchanging it and see if a different device works. if not i would suggest contacting sandisk support and send them the logs from the iXpand so they can take a look and see what may be the root cause.