Niagara mesh renderer of UE4.27 cause gpu hang error (IOAF code 3) on iOS13

iOS13 doesn’t support shader validation, and iOS14 or higher doesn’t have this problem. All I know is that reading a float buffer in GetFloat function cause that problem, because if I return a constant value or the index used to read the buffer, or any float value else, the crash won’t happen, but I can’t find out why reading a float buffer can cause GPU hang error.