NAV button changing CDI?!?

Why am I surprised but I'm seeing totally odd behavior here.

First pic.  I've used the DIR page to attempt a direct to MISEN.  In pink, then press EXEC to confirm it.  The CDI needle is centered.

Pic two.  I press NAV button the AP to fly direct to MISEN... the CDI mysteriously shows me left of course simply by pressing the button!  Very odd.  

Now if I press the preset button to cycle off of FMS to another nav source (in my case VOR2), then back to FMS, the CDI centers again!

What gives?