SpriteKit fillTexture different results in TestFlight

I have a screen in an app that uses SpriteKit to display items that should look kind of like bubbles. When I'm testing it with the simulator or my real device everything looks fine. However when I install the app through TestFlight the appearance is very different.

This is how it should look and it is running directly from Xcode:

and this is the installed app:

I'm using a semi-transparent png image to achieve the 3D look. Here is the debug view hierarchy:

So it's a SKShapeNode with a SKTexture added as a child of the main node.

It appears also that the View Hierarchy looks similar to the TestFlight one but I guess I shouldn't rely on that as it's not a real rendering the way it's on a device.

I tried to change blending which completely changes the look and the results are again different locally and installed. Tried changing the rendering mode as well but it's still the same.

Any idea why it looks different and how can I know which appearance it will be when released on the App Store?