Paper2d Textures get black after several times restarting the game

Hello,

im working on my first Paper2d Android Game. Its an endless runner, based on this official Tutorial from Epic Games. (https://www.youtube.com/watch?v=yS-yQfo0lc0&list=PLZlv_N0_O1gbY4FN8pZuEPVC9PzQThNn1)

After i start the game and press play the tilemaps will spawn in front of the character and will be destroyed after he reaches a specific point.
When the character dies (collision event), some variables get saved and the blueprint command to open a new level is fired to get to the main menu again which is kept in an own level.

This works fine the first few times i press play, but after 3-4 times (its random) the textures of the level objects keep black. I made two screenshots of the scenario.
One before and one after the bug.

To get the textures normal again, i have to stop the whole process of the game manually on my device and delete the cache. But strangely that not ALWAYS helps. Sometimes i have to do this two times before the game will run again as it should…

Screenshot_20170326-181645.png

Screenshot_20170326-181759.png

The reason i posted this in the Android Section is, that this bug only sets in when i play it on my Smartphone device. When i play the Game several times in the Unreal Editor itself nothing goes wrong.

I hope that anyone maybe has an idea, what the problem of this could be.
I looked up several options in the Project Settings but im not sure which one could have an effect.

The project is packaged as an ETC1 . But i tried ETC2 too, and this doenst make a difference.