You can just post the bit's part number Woody and one of us can post the image. The reason it's dipping at the end may be because the fences aren't lined up with each other. It can also be because you have too large a gap between them and the pressure you are putting on it is causing it to dip in. Another problem if the piece is riding against the fence on the beads is that when the trailing edge passes the first fence the piece is dipping because the bead is narrower than the face of the uncut board. Without more info that would be my best guess. It's not easy to set up any round profile bit so that it only cuts just to the face of your board and not deeper without leaving a small flat on the top of the bead. I've found that the best tool to set the fence with when using bits like that or a bull nose is to use a round dowel of close to the same diameter.
If that last possibility is the issue then one solution is to attach another board on top of the one you're beading. The top one will stay registered against the fence and prevent the bottom one from dipping. You can attach it with double sided carpet tape or a few drops of hot melt glue. My preference would be the hot melt. It's easy to clean up after with a sharp chisel or utility knife. It's also cheaper in the long run.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.