Chemistry Between Chuck + Sara

Hi All,

New to the board and I was lucky enough to discover Chuck recently; sad to say I did not watch the show during its original run.

First, I love the show; it has become my overall favorite show, for many reasons. With that said, please know that I am not criticizing anyone or anything but I do have an observation and a question...

The actor/actress that played Chuck & Sara had wonderful chemistry, almost magical. Through most of the series their kisses felt real and genuine, I could almost feel their love. Later in the series their intamacy felt forced and fake, especially when kissing... Again, not criticizing but I'm wondering if anyone else noticed this or if I am just seeing something that is not there... What happened to their chemistry?