Hey Crocopede,
I have just ran a couple tests to see if I could run across the error that you were seeing but i was unsuccessful. Would you be able to share your project or the asset with me so that I may be able to recreate the issue? You can send it to me privately through the forums if you would like. Here is a link to my page: https://forums.unrealengine.com/member.php?4890-Sean-Gribbin.
If you don’t wish to share your project, is there a step by step way that I may be able to reproduce this issue?
Also, be sure to let me know how the Android test goes with the UMG.
Thanks!