I had the same issue as Chi Phan. And did some investigation.
what eventually helped me, was translating my labels using the online editor: https://xliff.brightec.co.uk
But i think its down to formating of the label .xlf files.
Heres something to try out, if you want to dive deeper into the issue
1. Go to your project settings > labels
2. Using the drop down set your labels to "English", with the built in label set
3. Now click the button "Create new".
4. In this new label set, lets rename "START COURSE" to "BEGIN COURSE"
5. Now if you download this label set (click the dropdown, and hover over your button set, you get an icon to download the label set).
6. If you open this file in notepad and search for "courseStart", you will see the line:
<trans-unit id="courseStart"><source>BEGIN COURSE</source>
So it looks like it did in fact chance the text to "BEGIN COURSE", but if you load this label set from this file, it changes back to "START COURSE".
Now if you edit your file in notepad again and modify the above line to:
<trans-unit id="courseStart"><source>BEGIN COURSE</source><target>BEGIN COURSE</target>
what i did was just to add: <target>BEGIN COURSE</target>
Now save this file and load this file instead.. now it works!
So i suspect this to be a bug. And hope for it to be fixed.
Hope this helps anyone stumpling upon this post! :)