This is probably going to be the most annoying LAG bug of all time. Yes, it's caused by lag and server overload. What the bug is, is when you beam down on a planet, your in ship form, you wait a little bit and your in human form. This however is where missions become difficult, because YOUR BY YOURSELF IN MISSIONS, AND YOU CAN NOT CALL FOR BACK UP.
I'm sure the Dev's know this by now, but don't know what cause's it, I'm telling you, this only happens during peak hours or when the servers are full. Thus, it's caused by lag and servers not responding.