Matt:
Thanks for the heads up.
I have the layout in a spare room in my house plus I screw down all track. Hopefully this will alleviate the issue. But I will monitor and see if anything happens. One thing I did notice. The joiners are pretty flimsy. Once inserted they will break if you need to remove for any reason.
The yard will be the only place I use these joiners. Everywhere else (especially the main lines) when I go from Atlas to Ross I will use the undercut method you mentioned. Since I am screwing down all track I have been thinking about just butting the ends together w/o any joiners at all. Power / ground will be connected on both sides. This method works for isolated ground track plus going form one power break into another. Your thoughts Matt?