Yep, I spotted that the first time my mill head "fell out of tram". What surprised me is just how quickly - and how far - out it went. And I thought I had a nice rigid machine in the Bridgeport...
Lesson learned - I now check my tram much more regularly, although today I managed to produce a rectangular block that was accurate to within less than 0.001" on all sides, which I was chuffed about. Shame it's not something more useful than just a block....