Howdy Dredok,
Thank you for reporting this issue. I have been attempting a reproduction of the issue and have been unsuccessful so far. Here is how my Blueprint Widgets set up:
Please let me know if you have your BP’s set up any differently then mine currently are. I have been testing on the currently release 4.5.1 and later build of the engine and have been able to play on mobile preview with no issues.
Thanks and have a great day!