WM22: iOS with IW_ and ..Planes

In our project we use Internal Windows and ..Plane
Somehow this crashes on iOS device ... not on Mac emulator and not on Android.Device

This crash only happens when we use a looper containing images on an Internal Window and only when we go back from that Internal Window using IW_xxxx..plane = ....

in Xcode I get a pointer error: "Tread 1:EXEC_BAS_ACCESS (Code=2, address = 0x6c0001..."

We use Xcode 9.2 en WM22 (Can i use 9.2 with WM?)

Do you have (the same) experience?

Regards, Aad