Sergey, that looks like it is a bug. I tried testing with a layout where one side is responsive, and the other side with panels and Google Map on both of them it rendered fine. But when using tabs, and switching to the one with a panel, it does not render. If you view your Mashup and open dev tools (F12) and switch to the network tab, you can see that the Map does not get called when you switch tabs. Would it be possible for you to open a support case for this?