How to run a shell script on Ubuntu-touch?

I want to run a shell script on my "bq Aquaris E4.5 Ubuntu-Edition" phone in the Terminal App and created a shell script in /home/phablet/Documents/sync.sh

#!/bin/sh
# sync contacts and calendar with OwnCloud
syncevolution owncloud calendar-defaultcalendar
syncevolution --sync slow owncloud contacts
exit 0

The script is executable but returns:

bash: ./sync.sh: /bin/sh: bad interpreter : Permission denied

I'm not sure what interpreter runs on Ubuntu-touch (bash, sh, ??)
and I'm also not sure what rights the default user has.

So what's wrong or missing?

Looks like a bug in the ubuntu-terminal-app.

The bug description mentions a workaround:

It seems to work when I use bash ./testscript.

The ./ is optional