In your example part you need to change the stopping condition on the check surfaces between DS-CS and PS-CS tangency when you get to the fillet between the two floor faces. I attached a sample.
Hope this is what you are looking for. Glad to see somebody else still giving Sequential Milling some use. It is a very powerful way to machine.
Sometime Seq Mill more flexible. Of course, for this sample will be enough Fixed Contour or Planar Mill, but I have a lot of samples whrere Seq Mill is a last way to reach result. For example, I have some projects for SAPHIRE (!) milling&grinding, no any chance without Seq Mill, even for 3 axis operation. If I need to mill Rectangular web, and I need TURN ON cutter compensation just for one side only - I cannot to do it without Seq Mill..
SEQUENTIAL MILL - FOREVER! (I remeber this method from Unigraphics (not NX) version 10.5, no any changes. It is a sign - good method.)