I solved it!
I just saw this post:
https://community.cesium.com/t/solved-ios-apps-distributed-to-the-app-store-crash/29401
and reading that and looking at my device output and it looked like a similar pointer issue.
https://alyamkin.artstation.com/blog/9VEQ/ue4-ios-and-pointer-being-freed-was-not-allocated
So i just did the fix from that post and it worked like a charm!
thx-e