Subfigure environment \label and \ref are not operating correctly.

[Thanos]

Recently I came across with a problem that I think it is a bug of the system. I was trying to create a beamer presentation and by using \usepackage{subcaption} and \begin{subfigure} environment. While I was trying to use the \label and \ref points to my subfigure(s) I noticed that only the first \label was operating correctly as 1a. Unfortunately the rest are coming up as ??. I assume this is because the \ref points are located before the \label, but in this case all of them should not be operating correctly all should fail.

I was not able to find an answer relative to my question no matter how much I searched for. Maybe it is a bug of the system. I was just hopping that you could provide more information and maybe a solution to overcome this problem.

I have also attached the code as bug.tex, the file is in executable format. You need to include to picture files to run.

I am using the (This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013/Debian) restricted \write18 enabled).

Since this is the first time that I am submitting a bug please bear with me if I am missing something.

Thanks in advance for your time and support to the users.

Best Regards,
Thanos