SDK Images not visible in Testflight Build

I'm working on an SDK Which is being used by several other teams for their product in our company. When they test their product in simulator and also on real devices, everything looks fine. But when it comes to TestFlight, some images from the SDK are not Visible in the UserInteface. All those images that are not visible in testFlight are being assigned in storyboard and not in code. Tried many solutions and cross checkings like image assets filename in Xcode and Finder, but was not able to find a solution.