Iphone WebGL Material Bug

We are AR developers who using Zappar Studio. When on a project we got a small bug on iphone webGL platform. As you can see in the attachments one of photo on ZapparApp and the syringe work very good. But in other photo on Iphone WebGL and some problems in the behind of blue side of syringe. We don’t see any problem on android and we can not fix this problem. Could you help us for this bug if you know how to fix it. Thanks in advance, good work.