Generally, cross-platform testing is compatible with multiple platforms, but one can face cross-platform testing issues. The issues depend upon the different OS/device versions. You can see that the same application works on one OS while it might not work on another version.
For example, we have faced an issue that our application was working fine on iOS 6.x version devices but on tapping a few modules on iOS 5.x devices, the application crashes. The same thing happened with 2.3.5 Vs.